491 ECHO SOUNDER

INSTALLATION MANUAL
Rev A Part Number GM495 Northstar
a unit of Brunswick New Technologies Marine Electronics
30 Sudbury Road Acton, Massachusetts 01720
www.NorthstarNav.com Service: 978/897-6600 Sales: 800/628-4487

Table of Contents

SECTION ONE Introduction - - - Welcome to the Northstar 491 Who should read this manual Scope of this manual - - - - Installation considerations - - 26
SECTION TWO Installing the transducer Safety considerations - - - - - - Selecting a transducer - - - - - - Installation considerations - - - - Choosing a mounting location - - Installing the transducer - - - - - Maintaining the transducer - - - SECTION THREE Installing the 491 Safety considerations - - - - - System components - - - - - - Choosing a mounting location - Mounting the 491 - - - - - - - Wiring the 491 - - - - - - - - Initial checkout - - - - - - - - Installation test checklist - - - -
SECTION FOUR Troubleshooting and servicing the 491 Common 491 installation problems - - - - - - - The status LED - - - - - - - - - - - - - - - - Getting technical support - - - - - - - - - - - Ordering replacement parts - - - - - - - - - - Servicing the 491 - - - - - - - - - - - - - - - Returning a 491 for service - - - - - - - - - - APPENDIX A Technical specications
- - - - - - - - - - - - - - 27
Glossary - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 29 Index - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 31

SECTION ONE Introduction

Welcome to the Northstar 491
An echo sounder is a device that provides information about the water directly beneath a vessel. The Northstar echo sounder system consists of:
the Northstar 491 echo sounder sensor a Northstar navigation system such as the 962, 958 or 6000i a transducer
The 491 can be used with either a single-element transducer or a dual-element transducer. The 491 automatically pings both transmitters at power-up to determine the number of transducer elements connected. If a single element is detected, the 491 operates in single-frequency or dual-frequency interleaved mode (as determined by the operator) at 600 Watts. If two elements are detected, the 491 uses both elements at 1000 Watts. Installation and setup procedures are different for the two basic types of Northstar navigators. The following terminology should be carefully followed:
the term 961/962 indicates instructions that apply to the Northstar 961 and the 962 navigators the term 957/958/6000i is used for these units the term navigator by itself identies information that applies to all units
Who should read this manual Scope of this manual
This manual is for marine technicians who are installing the Northstar 491 and connecting it to a Northstar navigator and a transducer.
In this manual, youll nd information about the following:
mounting and wiring the 491 connecting the 491 to the Northstar navigator installing a transducer (an overview is provided, but for such details as wiring, see the documentation provided by the transducers manufacturer)
491 INSTALLATION MANUAL Revision A

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connecting the 491 to a transducer (see also the Transducer Connector InstructionsGM492) troubleshooting and testing the system technical specications for the 491
For information about obtaining technical support and returning the 491 for factory service, SECTION FOUR Troubleshooting and servicing the 491 beginning on page 21. For details about operating the 491, see the Northstar 491 Echo Sounder Operations Manual (GM494) or Northstar 6000is Reference Manual, for that product.
Installation considerations

CAUTION!

The following list of installation considerations isnt a substitute for all the details in Section Three. To ensure that you meet all critical installation parameters, be sure to read that entire section and follow all of its recommendations.
1. Check the shipping carton for any damage, and immediately report any damage to the carrier. Save all packing material in case you have to return the 491 to the factory for repair or evaluation. 2. Unpack the carton, and check its contents. You should have received: the Northstar 491 Echo Sounder 10-foot (3-meter) data cable to connect the 491 to the navigator 10-foot (3-meter) power cable for the parts kit (containing transducer cable end connector, backshell, heatshrink tubing, and the Transducer Connector InstructionsGM492) Northstar 491 Echo Sounder Installation Manual (GM495) Northstar 491 Echo Sounder Operations Manual (GM494) owner registration card 3. Fill out the owner registration card and mail it to Northstar. 4. Review all of the installation requirements as outlined in Sections Two and Three. 5. Install the transducer, then terminate the cable (see Connecting the 491 to a transducer starting on page 18). 6. Mount the 491. For instructions, see Mounting the 491 beginning on page 14. 7. Connect the 491 to ships power and to the navigator. Connection information begins on page 15. With the vessel in the water, turn on the system and verify proper operation.

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SECTION TWO Installing the transducer

Safety considerations

WARNING!
Be sure to turn the power off before starting the installation. Further, it is highly recommended that you keep power off while youre performing the installation. If power is left on or turned on during the installation, fire, electrical shock, or other serious injury may occur. Be sure to ground the equipment to prevent electrical shock and mutual interference. Be sure the transducer outputs are tied together before handling to avoid electrical charge build-up.
Be sure to use a 3-amp fuse. Using the incorrect fuse can result in fire or damage to the 491.
Mounting the transducer requires drilling holes through the hull; make sure the installation does not cause the vessel to leak. A thru-hull installation should be performed by a professional installer. Do not attempt this unless you are fully qualified. Do not perform a thru-hull installation of the transducer when the vessel is actually in the water. Immediately after installing the transducer, be sure to check for leaks, and dont leave the vessel in the water for more than three hours before checking it again. Northstar assumes no responsibility for improper installation of a transducer.
Be sure that the transducer doesnt interfere with any of the on-board systems. Check all other systems to ensure that their performance doesnt degrade when the transducer is connected.

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Selecting a transducer
Northstar recommends using an Airmar transducer with the Northstar 491 echo sounder. The Airmar B260, B744 and P66 can be obtained from Northstar as an installation kit with connectors installed.
Table 1: Northstar-recommended transducers
Manufacturer Airmar Airmar Airmar Housing B260 B744V/B44V (with 3-wire speed) P66 Power 1 kW 600 W 600 W Frequency 50/200 kHz 50/200 kHz 50/200 kHz Northstar P/N TD1004 TD1005 TD1006
A table of Airmar transducer elements is given below to assist in evaluating characteristics of other Airmar transducers.
Table 2: Airmar transducer elements
Transducer element Single or Dual element Single Used in Airmar P/N B744V B744VL P319 B117 SS555 P66 P79 P74 B256 B45 B250-B B260 Acoustic material Beam Width (50 kHz) 45 Beam Width (200 kHz) 12 Rated Power

50/200A

Urethane

Single

50/200B 50AE/200Riq

Single Dual

Urethane Urethane

1200W 1000W

Dealers can also purchase quantities of transducers directly from Airmar Technology Corporation at: Airmar Technology Corporation 35 Meadowbrook Drive Milford, New Hampshire 03055-4613 Phone 603/673-9570 Fax 603/673-4624 (www.airmar.com)

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The following basic setup information isnt a substitute for the installation instructions provided by the transducers manufacturer. To ensure that you meet all critical installation parameters, be sure to read and follow all of the requirements in their instructions. Northstar assumes no responsibility for improper installation.
Choosing a mounting location
Do not mount the transducer: behind strakes, fittings, or hull irregularities (mounting in those locations may increase turbulence, aeration, and cavitation) or near the keel near openings for water intake or discharge where it might be loosened by the vessels vibration less than four feet away from the Northstar 961/962 processor or other similar equipment to minimize interference
The two most common problems with echo sounder installations stem from electrical noise and cavitation. Either of these situations can produce poor performance. Electrical noise occurs when the transducer cable is routed too closely to noise-producing electronics, such as alternators, AC generators, radars, etc. To avoid problems with noise, route the transducer cable by itself (not in a bundle) and away from other wires or cables and the engine. Cavitation can occur at high speeds. During cavitation, bubbles form between the transducer and the water. When this happens, the transducer cant get its energy into the water properly and wont be able to detect any echoes. To avoid cavitation, choose a mounting location with good water ow all around it at all speeds. Choose the mounting location to obtain the best possible performance from the transducer and the 491. Take into account the vessels maximum speed when selecting a mounting location, as turbulence can affect echo sounding capabilities. Before any drilling or cutting takes place, carefully choose a mounting location for the transducer that meets the following criteria (also see Figure 1 on page 7), depending on the type of vessel:

the transducer is more than four feet away from the Northstar navigator and other similar equipment, to prevent mutual electrical and magnetic interference the transducer and its cable are as far as possible from other electrical cables there is space above the transducer for the transducers stem, housing, and cable

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the path for running the transducers cable is reasonably directkeep in mind that the transducer cable is 33 feet long (10 meters). To prevent damage, coil any excess cable and secure it water turbulence and noise are minimal, decreasing the amount of bubbles passing over the transducer face the transducer isnt behind hull irregularities or near eroding paint; both indicate areas subject to turbulence the transducer is as far as possible from the engine or propellers, and inboard of the lifting strakes the transducer always remains submerged and parallel to the water surface the transducer is easily accessible from inside the vessel for adjustments and maintenance the transducers ultrasonic beams arent obstructed by the keel, propeller shafts, or any other part of the vessel the hull thickness falls within the limits in Table 3 below (all dimensions are perpendicular to the waterline):
Table 3: Hull thickness limits
Model AirMar B44V/B744V with fairing AirMar B44V/B744V without fairing AirMar B260 with fairing AirMar B260 without fairing Minimum 6 mm (1/4 inch) 6 mm (1/4 inch) 19 mm (3/4 inch) Maximum 19 mm (3/4 inch) 65 mm (2 1/2 inches) 45 mm (1 3/4 inches) 114 mm (4 1/2 inches)

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pressure waves
1/3 aft LWL (Load Waterline Length) displacement hull 150-300mm (6-12")
outboard and I/O planning hulls inboard

step-hull

fin keel sailboat

full keel sailboat

Best location for the transducer
FIGURE 1: Recommended installation locations for a transducer
Installing the transducer
A at-bottom hull provides the best environment for mounting the transducer: It provides a horizontal surface and a constant water ow over the transducer, with little turbulence (see Figure 2 for the recommended transducer incline angle). If the vessel has a deadrise angle greater than 5 degrees, mount the transducer on a fairing block to create a horizontal surface and keep the transducer perpendicular to the waterline (see Figure 3). You must order the fairing block, if needed, from the transducers manufacturer.

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3 incline angle
1/3 aft LWL (Load Waterline Length)
FIGURE 2: Recommended transducer incline angle

backing block

slope of hull deadrise angle parallel to waterline fairing
fairing thickness at narrowest point 612mm (1/41/2")

multisensor

Deadrise angle and fairing thickness (B44V shown)
FIGURE 3: Typical nished thru-hull installation with a fairing block (Airmar B744V)
Maintaining the transducer

Using anti-fouling paint

Do not expose the transducers face or plastic housing to gasoline or strong solvents, such as acetone. These solvents can penetrate and degrade many plastics and reduce their strength. The transducer should be coated with water-based anti-fouling paint to prevent aquatic growth.

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housing

paddle wheel insert

Paint exposed housing and bore up 30mm (1-1/4")

detail

lower O-ring
Paint outside wall below the lower O-ring including exposed end, paddle wheel cavity and paddle wheel
Anti-fouling paint (B744V shown)
FIGURE 4: Anti-fouling paint areas (for Airmar B744V)
Use special transducer paint. Other paints may contain copper, which is conductive and can burn out the transducer within minutes!

Cleaning a transducer

To clean the transducer of heavy debris or foul sea growth, use a stiff brush or putty knife, but dont scratch the surfaces. Check the transducer every few weeks, maximum. Use sanding sparingly, as repeated sanding may affect the transducers performance at high speeds. For lighter cleaning, the surface may be wet-sanded with #220 or ner wet/dry sandpaper.

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SECTION THREE Installing the 491
Be sure to turn the power off before starting the installation. Further, it is highly recommended that you keep the power off while youre performing the installation. If power is left on or turned on during the installation, then fire, electrical shock, or other serious injury may occur. Be sure to ground the equipment to prevent electrical shock and mutual interference. Be sure that the voltage of the power supply is between 10 and 36 volts DC. Connecting to the wrong power supply can result in fire or damage to equipment. Be sure to use a 3-amp fuse. Using the incorrect fuse can result in fire or damage to the 491.
Keep the following safe compass distances from the 491: 1.0 m standard, 0.8 m steering.

Be sure that the 491 doesnt interfere with any of the on-board systems. Check all other systems to ensure that their performance doesnt degrade when the 491 is turned on. If the vessel is out of the water when the echo sounder is turned on, the transducer may be damaged.
Do not open the 491. There are no serviceable parts inside. Unauthorized tampering with the unit will automatically void the warranty.
Do not mount the 491 in the bilge. It is not designed to resist heavy exposure to water and chemicals.

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System components

Figure 5 on page 13 shows a congured 961/962 echo sounder system, and Figure 6 on page 13 shows a congured 957/958/6000i echo sounder system.

GPS Antenna

Northstar 961/962 display
10-foot data cable (Northstar-supplied) Northstar 961/962 Processor 10-foot power cable (Northstar-supplied) Northstar 491 Echosounder 33-foot cable (Part of transducer) Transducer

Ships Power

Figure 5: Echo sounder system components with the Northstar 961/962
10-foot data cable (Northstar-supplied) Northstar 957/958/6000i Navigator 10-foot power cable (Northstar-supplied) Northstar 491 Echosounder 33-foot cable (Part of transducer) Transducer
Figure 6: Echo sounder system components with the Northstar 957/958/6000i

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Before any drilling or cutting takes place, carefully choose a mounting location for the 491 module that meets the following criteria:
where the transducer cable is kept securely away from other wires where the path for running the required electrical cabling is reasonably direct; keep in mind the different cable lengths where the 491 wont be exposed to water where the status indicator (on the front of the 491) can be observed for system testing and troubleshooting.
NEVER MOUNT THE 491 MODULE IN THE BILGE!

Mounting the 491

Figure 7 shows the mounting dimensions for the 491. The 491 may be mounted either horizontally or vertically. The mounting template supplied with the unit may be helpful in planning the installation and locating the mounting holes. The keyhole slots make installation in hard-to-reach areas easier, but be sure to tighten all mounting screws securely. Leave room for installing and removing cables.

0.190 dia. 0.360 dia.

8.78 5.80 2.90 2.90

491 Echo Sounder

BNT Marine Electronics 30 Sudbury Road Acton MA 01720 800-628-4487 www.NorthstarNav.com

6.24 7.22

#2 Speed +V #3 Speed Gnd #7 Thermistor #6 Depth Lo #9 Depth Shields

TRANSDUCER

836 VDC 8 Watts
Allow space for cabling from connectors.

STATUS

#1 Speed Sig #4 Thermistor #5 Depth Lo + #8 Depth Hi + #10 Depth Hi

0.190 dia.

Dimensions in inches
FIGURE 7: 491 mounting dimensions and connector locations

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Wiring the 491
Make sure that fuse or circuit-breaker protection is provided at the power source.
The majority of installation problems are caused by shortcuts taken with system cables. When installing the 491, be sure that you:
assemble connectors carefully dont make sharp bends in the cables leave service and drip loops, so that moisture wont run down the cables and into the 491 or the navigator tie-wrap all cables to keep them secure if cables are shortened, lengthened (not recommended), or re-terminated, seal all wiring splices prevent interference from the transducer cable
Electrical power requirements Connecting the 491 to ships power
The 491 is a negative-ground system that is reverse-polarity and overvoltage protected. The unit requires 8 to 36 VDC power at 8 Watts.
The connection between ships power and the 491 requires the 10-foot (3-meter) power cable supplied with the 491. The wires in the power cable must be connected as follows (black and white can be connected together at the power source):
Red Positive (+) (fused lead) Black Negative () Green Ground (earth)
The 491 should be grounded to the vessel to eliminate interference. Secure the green wire to the vessels nearest grounding point. Without an earth grounding, performance may be degraded.
Connecting the 491 to the 961/962
The connection between the 961/962 and the 491 uses the 10-foot (3-meter) data cable supplied with the 491. The cable connects to the P1 slot on the back of the navigator. The cable is shipped with a round 6-pin connector that attaches to other Northstar navigators. To install the 491 with a 961 or 962, you must cut off and discard the 6-pin connector, and wire the cable as shown below. Be sure you dont cut off the 8-pin connector that plugs into the 491! Figure 8 below illustrates the wiring at the 961/962 end of the cable. Table 4 describes the pins functions.

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961/962 P1 Connector Plug (Wiring Side View)
Orange White Violet Brown Black Blue Red (not connected) Data Cable
FIGURE 8: Interface cable connection from 961/962 to 491
Table 4: Cable connection between the 961/962 and 491
961/962 pin number 11 12* 12* ** 961/962 P1 signal name Port 3 In (A) Port 3 In (B) Ground Port 3 Out (A) Port 3 Out (A) Port 3 Out (B) Ground Not connected Cable wire color Blue Black Brown Violet White Orange Green Red
* Connector P1, pin 12 on the 961/962 requires two connections from the cable. **The red wire is not connected on the 961/962 end, and should be insulated and capped.

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Connecting the 491 to the 957/958/ 6000i
The connection between the 957/958/6000i and the 491 requires the 10-foot (3-meter) data cable supplied with the 491. The cable connects to the AUX port on the back of the navigator. The cable is shipped with the connector installed the following information is provided for cases where it is necessary to remove and reinstall the connector. Figure 9 below illustrates the wiring for the navigator end of the cable. Table 5 describes the pins functions.
Brown (pin 1) Green (pin 1) White (pin 2) Blue (pin 6)
Orange (pin 5) Violet (pin 4) Black (pin 3)
Figure 9: Interface cable connection from 957/958/6000i to 491
Table 5: Cable connection between the 957/958/6000i and 491
navigator pin number 1* 1* 6 AUX port signal name Shield/Gnd Remote On Gnd Remote On input NMEA AUX In (B) NMEA AUX Out (A) NMEA AUX Out (B) NMEA AUX In (A) Cable wire color Brown Green White Black Violet Orange Blue
* Pin 1 on the 957 AUX port requires two connections from the cable. The red wire is not connected on the navigator end, and should be insulated and capped.

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Connecting the 491 to a transducer
Transducers purchased from Northstar (see page 4) are shipped with a connector installed. The following information is supplied for transducers purchased elsewhere and for cases where it is necessary to remove and reinstall the connector. CAUTION!
High voltage is present on the transducer wires!
Figure 10 and Figure 11 below show how to install the connector on the cable. 1. Slide the heat shrink tubing onto the transducer cable. 2. Slide the connector backshell onto the transducer cable. 3. Prepare each wire for insertion into its solder cup by stripping it as shown below and tinning it. 4. Carefully solder each wire to the appropriate cup as specied in the table. 5. Slide the backshell down the wire and screw it onto the connector body. It should be hand-tight. 6. Using the supplied screws, screw the strain relief onto the backshell. 7. Slide the heat shrink tubing onto the connector. Be sure to leave room for the locking collar to retract. 8. Heat the shrink tubing until it shrinks around the connector providing a watertight seal.

Setting up the echo sounder
Youll need to set the echo sounder display options on the navigators ECHO SOUNDER SETUP screen. Press the STAR key to display this screen and set these options. For details, see the Northstar 491 Echo Sounder Operations Manual (GM494). To turn off the 491, turn off the navigator by pressing and holding PWR until the screen goes dark. The 491 will turn off automatically.

Turning the 491 off

Installation test checklist
If the vessel is out of the water when the echo sounder is turned on, the transducer may be damaged. Perform all tests on the with the vessel in the water.
1. Make sure the vessel is in the water. 2. To test the system after installation, turn on the navigator and conrm that power is on with no errors. If echo sounder data isnt moving across the ECHO screen from right to left, see Common 491 installation problems beginning on page 21.

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SECTION FOUR Troubleshooting and servicing the 491
Common 491 installation problems The status LED
Typical problems you may encounter either during or after the 491 installation process are outlined in Figure 12 on page 22 and Figure 13 on page 23. In the 961/962, the diagnostics screen may also help pinpoint a problem.
The two-color LED located behind the 491s front-panel STATUS window displays the units current condition. The LED presents the following information:
solid green: System has power, self-test passed, and communicating with navigator. Flashing green: 491 is not communicating with the navigator. Red: Self-test failed

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SECTION FOUR Troubleshooting and servicing the
No echoes displayed when STAR key is pressed.
Is the Advance Speed set to zero?
Change the Advance Speed setting.
Contact Northstar Service to upgrade to the latest version of 961/962 software.
Is the 961/962 software Version 3.0 or greater?
Configure NMEA Port 3 for the 491. See the Initial checkout section of this manual.
Has NMEA Port 3 been configured for the 491?
YES 491 is communicating with the navigator Check the 491's STAT indicator STEADY GREEN 1. Check transducer connector for the proper wiring. 2. If wiring is correct,check transducer impedance with an ohmmeter. 3. If the transducer is open or shorted, replace it
1. Check fuses and circuit breakers 2. Check power to 491 with a voltmeter. 3. Verify that the data cable between the 961/962 and the 491 is properly wired and connected.
FLASHING GREEN The 491 and the 961/962 aren't communicating properly. Check the wiring of the data cable between the 961/962 and the 491.

There's a hardware problem with the 491.
Figure 12: 961/962 echo sounder system troubleshooting

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No echoes displayed on sounder screen.
Configure the navigators Aux Port for the 491. See the Initial checkout section of this manual.
Has the navigators Aux Port been configured for the 491? YES 491 is communicating with the navigator.
1. Check fuses and circuit breakers. 2. Check power to 491 with a voltmeter. 3. Verify that the data cable between the navigator and the 491 is properly wired and connected.
Check the 491's STAT indicator

STEADY GREEN

FLASHING GREEN The 491 and the navigator aren't communicating properly. Check the wiring of the data cable between the navigator and the 491.
1. Check transducer connector for the proper wiring. 2. If wiring is correct,check transducer impedance with an ohmmeter. 3. If the transducer is open or shorted, replace it
Figure 13: 957/958/6000i echo sounder system troubleshooting

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Getting technical support
You can E-mail the Service Department directly from Northstars website (www.northstarnav.com). Here, you also can access additional technical information under either the Manuals link (you can download manuals in PDF form) or Support link.
After youve followed the instructions in this manual, if you need additional technical or operations support for the 491, or if you have any other service-related questions, you can contact either your dealer or the Northstar factory. You can reach the Service Department by E-mail, fax, U.S. mail, or phone as described in Table 7 below.
NOTE: Please have the following items available when you contact Northstar.
the 491s serial number, located on the top of the unit the transducer manufacturers name and the transducers model and part number
Please be as complete and accurate as possible when describing the problem so that a service technician can research the problem and provide the quickest response. The Northstar Service Department is available between 9:00 AM and 5:00 PM Eastern Time, Monday through Friday, excluding major holidays. If you have questions about purchasing parts or nding an authorized Northstar dealer, or if you want basic product information and brochures, contact the Northstar Sales Department as described in the table below.

Table 7: Contacting Northstar
Email: Service: service@northstarnav.com Sales: sales@northstarnav.com Fax: Service: 978/897-1595 Sales: 978/897-7241 Telephone: Main number: 978/897-6600 or 800/ 628-4487 Sales: 978/897-0770 Service: 978/897-6600 U.S. mail: Northstar 30 Sudbury Road Acton, MA 01720 Website: www.northstarnav.com (you can send E-mail to Northstar directly from this site)

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Hearing from you
Your feedback is important and helps Northstar ensure that this manual is a valuable resource for all marine technicians. Send your questions, comments, or suggestions about this manual to: docs@northstarcmc.com
Ordering replacement parts Servicing the 491
To order spare parts or replacement/missing parts, call the Sales Department at 978/897-0770.
Repair of the 491 is performed only at the factory. Service includes a complete hardware and software check-out. NOTE:
Field repairs are not authorized and will void the warranty! For transducer service, including parts and repairs, please contact the transducer manufacturer.
The 491 and any accessories returned for warranty repair that are determined to be without fault are subject to a handling charge.

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Returning a 491 for service
Before returning the 491 to the factory, to prevent delays it is critical that you first obtain a Return Materials Authorization (RMA) number from the Northstar Service Department. If the 491 was purchased through a dealer, call the dealer with the 491 serial number so they can help you get an RMA number. The 491s serial number can be found on the label at the top of the 491. Shipments without a proper RMA number will not be accepted!
If you have overnight or second-day shipping requirements, before shipping the 491, please call Northstar for turnaround time, freight charges, and payment arrangements. The 491 should be shipped only in a properly designed carton with packing material. Shipments to the Northstar factory should be made to the following address: Northstar Service Department 30 Sudbury Road Acton, MA 01720 USA
Return the transducer to its manufacturer, not to Northstar.

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APPENDIX A Technical specications
Table 8: 491 technical specications
Performance characteristics Frequencies Output power Pulse lengths Pulse repetition rate Alarms Update rate 50 and 200 kHz 1000 watts with dual-element transducers 600 watts with single-element transducers 0.1 to 2 ms 30 to 600 pulses/min Fish, bottom, and temperature 10 Hz maximum (depends on water depth) (up to 20Hz when used with the Northstar 6000i) Marker, bottom lock, bottom lock/center, bottom Fishing or cruising Shown on bottom of screen Single/dual frequency, split-screen, four zoom modes, A-Scope

Zoom modes Auto modes Navigation data Display modes Physical characteristics Dimensions Weight
8.78 x 7.22 x 2.35 inches (including backplate) 2 pounds
Environmental characteristics Temperature Standards Electrical characteristics 8 to 36 VDC, 8 watts, reverse polarity and overvoltage protection Transducer outputs protected against open circuit/short circuit -25C to +60C operating temperature -55C to +90C storage temperature Waterproof, sealed design meets the following: EN60529 IP65; EN60945 emissions; CE

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Table 8: 491 technical specications (Continued)
Manual controls Gain Clutter Signal level Noise limiter White level Range Advance speed Depth units Installation calibrations 0 to 75 dB 0 to to 5 ON/OFF Background color up to 3500 feet (1000 meters) 1/8 to 2/1 Feet, meters, fathoms Speed, temperature, gain, transducer depth/ offset

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Glossary

cavitation

The formation of bubbles, which may negatively impact a transducers readings by reducing its ability to put energy into the water. The rise of the bottom of a vessel above a horizontal line at the center of the vessel; that is, the slope of the hull away from the horizontal. An instrument that uses sound waves to measure the depth of a body of water or an object (such as a school of sh) below the waters surface. A block used to create a horizontal surface for mounting a thru-hull transducer when the vessels deadrise is more than 5 degrees. The device mounted through the hull to send and receive ultrasonic beams that determine seabed conditions and locate sh. Essentially, a transducer is an energy converter, which changes electricity to sound (send) and sound to electricity (receive). An imaginary column through the water created by the path of a single transducer ping and its echoes.

deadrise

echo sounder

fairing block

transducer

water column

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PAGE 30

Airmar Technology Corporation 4
Cable 491 and 961/491 and ships power to 957/958/6000i 16 Cautions installation 2, 3, 11 interference with tampering with the transducer 3, 5, 19 troubleshooting the wiring the 491 14, 17
Echo sounder components of system 1, 12 definition of 29 installation. See Installation, 491 serial number 26 setup options 19 specifications 27 STAT indicator light 18 turning off 19 turning on 18 wiring 14 Electrical power, requirements 14
Fairing block, definition of 29
Installation 491 cautions 2, 11, 14, 17, 19 connecting to 957/958/6000i 16 connecting to 961/connecting to ships power 14 electrical power requirements 14 general considerations 2 mounting dimensions 13 mounting location 13

How echo sounding works

An echo sounder produces high-voltage electrical pulses that the transducer converts into sound waves (called pings). The sound waves are sent downward through the water. When a sound wave hits and reflects off an object, such as fish, debris, seaweed, or the seabed, the reflected sound wave (an echo) returns back to the transducer along an imaginary vertical line called a water column. The transducer converts this echo into a tiny electrical pulse. The 491 digitizes these pulses and sends them to the navigator, so that echo sounding pictures of the water and seabed can be displayed and analyzed on the echo sounder screen. In essence, this system lets you see a real-time cross section of whats happening underneath your vessel. Figure 1, 957/958 echo sounder system components, below, and Figure 2, 961/962 echo sounder system components, below, show how the 491 connects to these navigators to enable echo sounding functions.

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GPS antenna
33-foot cable (part of transducer) 491 module

957/958/6000i Navigator

10-foot cable (Northstar-supplied)

Ship's Power

Transducer
Figure 1: 957/958 echo sounder system components
GPS antenna Control Head 33-foot cable (part of transducer) 491 module

961/962 Processor

Figure 2: 961/962 echo sounder system components
Page Echo Sounder Operations Manual
Powering the 491 on and off
As part of its power-up sequence, the navigator automatically activates the 491. The 491 is automatically shut off by the navigator when you press and hold PWR until the screen goes dark.

Setting up the 491

Your 491 should be installed by a qualified marine technician. Your satisfaction with the systems performance will be greatly influenced by the practical knowledge and experience of the installer. Unlike GPS or other marine electronics systems, echo sounder installation is as much an art as a science. The installation procedure includes setting up the following options: the transducers depth the speed and temperature the calibration for the speed sensor the calibration for the temperature sensor the gain calibration for the transducer
You may wish to change the following options from time to time to match your personal preferences: depth units (feet, meters, or fathoms) on the screen temperature units (Celsius or Fahrenheit) on the screen temperature scale (lowest and highest) on the screen (961/962 only) automatic saving of *FISH##* or *THERM##* waypoints when the 491 detects the presence of fish or a certain water temperature that youve set

Using 491 with the 961/962
Before starting, you should double-check that the 961/962s Port 3 is set to the 490 option: 1. Press STAR until you reach the SERVICE MENU screen. 2. Press PORT SETUP. 3. Press PORT 3.

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4. Check that the FORMAT option is set to 490. If not, set it now.
Using the 491 with the 957/958
Before starting, you should double-check that the navigators AUX port is set to the Sounder option: 1. Press STAR until you reach the OPTIONS/SERVICE INFO screen. 2. Press the PORT SETUP OPTIONS key. 3. Check that the AUX PORT option is set to Sounder. If not, set it now.

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Figure 3:

STAR key

ECHO SCREEN
Auto Picture Frequency Zoom Depth More
Depth settings More settings

Picture settings

Alarms Advance Speed Snapshot A-Scope Data Return
Shift Range Bottom box Return
Gain Clutter Noise Limiter Hue Signal level Return
Data on-screen Bottom box Temp box Temp graph Speed

Snapshot Display Rename

Alarm settings
Fish alarm Bottom alarm Temp alarm

Return

Archive Erase Return
Figure 4: 961/962 echo sounder menu structure

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Alarms Advance Speed Video A-Scope Data Return
Data on-screen Temp box Temp graph Bottom box Speed

Video setup Video on

Figure 5: 957/958 echo sounder menu structure

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Quick Start: Using the Echo Sounder
Displaying the echo sounders picture. 2-12 Using demo mode. 2-14 Introducing the displayed information. 2-15 Using automatic mode. 2-16 Changing the frequency of echoes. 2-17 Zooming in and out. 2-19 Setup functions. 2-22
This chapter showsofyou how tosounders important features. start using the echo sounder, and explains several the echo

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Displaying the echo sounders picture
Once the navigator has been configured to operate with the 491, youre ready to start viewing echo sounding data. To see the echo sounding screen at any time, press STAR from any screen. Youll see live echoes moving across the screen.
Depth marker and indicator Water temperature box Color bar Water temperature scale Frequency selection and indicator Depth box Echo data Depth Scale

Navigation information

Lat/lon of vessel

Dist/brg to waypoint

Steering indicator
Speed, course, and speed through the water
Figure 6: Illustrated ECHO screen
You can also review old echoes using Northstars SoundTrac feature. To activate SoundTrac, press the CURSOR PAD left or right on the ECHO screen. The position marker appears (controlled by the CURSOR PAD), and movement of echoes to the left stops. The data boxes at the bottom of the screen turn white and refer to the position marker rather than to your current position. Press the green LIVE DATA key to return to Page Echo Sounder Operations Manual

real-time echoes. For details, see Reviewing past echoes using SoundTrac starting on page 51.
Depth marker and indicator Water temperature box Color bar Water temperature scale Position marker and indicator Echo data Depth Scale

Depth box

Lat/lon of position marker
Dist/brg to position marker
Figure 7: Illustrated SOUNDTRAC screen

NOTES:

All of the alarm messages always appear on all of the echo sounders screens. You wont miss any alarms while displaying echo sounding data, and you never have to press any keys to view the current alarms (although you must press STAR to clear alarms that dont automatically clear). The SAVE and MOB functions always work normally. Moreover, on the 961/962, whenever you press either of these keys, the corresponding *SAVE##* or *MOB##* waypoints will be displayed automatically on the echo sounders picture, as well as on the CHART screen (after you press CHART).

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Using demo mode
The echo sounder can be operated in demo mode for training and familiarization. Simulated echo data generated by the 491 will be displayed. To enter demo mode: 1. Press STAR several times to display the ECHO SOUNDER SETUP screen. 2. Press the CURSOR PAD down to select demo mode, then press EDIT. 3. Press the CURSOR PAD left or right to highlight ON, then press ACCEPT. While in demo mode, the word Demo appears in the upper right corner of the ECHO screen. To leave demo mode, repeat this procedure, selecting OFF instead of ON.
Displaying echo sounder data on the CHART screen For the 961/962
You can overlay a smaller version of the echo screen onto the CHART screen.
To overlay the echo screen: 1. Press CHART to display the CHART screen, then press OVERLAY. 2. At the CHART OVERLAY SELECTION window, press SHOW 490. Both chart views A and B will display live echo sounder data on the right-hand side of the screen. 3. To remove echo sounder data, press HIDE 490 on the CHART OVERLAY screen.

For the 957/958

To overlay the echo screen: 1. Press CHART to display the CHART screen, then press SOUNDER. The CHART screen will display live echo sounder data on the right-hand side of the screen.

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Introducing the displayed information
The following information can be displayed on the ECHO screen.

Echo sounding

echo sounder data echo sounder frequency in use (50 or 200 kHz or both) A-scope automatic mode indicators (shing or cruising) manual operation indicator echo colors in use (the color bar at the far left) SoundTracs position marker for scrolling to old echoes water-depth digital display (on the left side of the screen) depth scale (on the right side) depth marker (press the CURSOR PAD to scroll the marker down) water-temperature digital display (if temperature sensor is connected; can be turned off) water temperature graph (if temperature sensor is connected; can be turned off) vessels current lat/lon (on the SOUNDTRAC screen, this lat/lon indicates the position markers location) vessels SOG and COG active waypoint, if any, and graphic steering indicator vessels Speed Through the Water (if speed sensor is connected; can be turned off)

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Using bottom lock/ center zoom
When you select bottom lock/center zoom, the sea bottom is flattened out and displayed in the center of the screen. You can see any fish near the bottom, as with the bottom lock zoom, and also examine the seabeds composition.

Using marker zoom

When you select marker zoom, you can choose the part of the water column to magnify. The top edge of the magnified area is determined by the location of the depth marker. To move

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the magnified area up or down, press the CURSOR PAD to move the depth marker.

Leaving zoom mode

You can return to the normal unzoomed display just by pressing and holding ZOOM for more than one second, or by pressing ZOOM repeatedly until you have cycled through all the zoom modes.

Setup functions

Several setup functions are available to configure the echo sounder to your preferences. CAUTION:
Be careful not to change any of the functions that are not described here unless you first read about them and understand their functions in the Northstar 491 Installation Manual.
Accessing the setup screen
To access the ECHO SOUNDER SETUP screen, press STAR several times until Echo Sounder is highlighted at the top of the screen.

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961/962 echo sounder setup screen
957/958 echo sounder setup screen
Entering numerical values
When changing the numerical value of the echo sounders settings, you can either press the CURSOR PAD to increase or decrease the value, or use the KEYPAD to manually type in the desired value.

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Transducer depth
This option specifies how far below the surface of the water the transducer is mounted. The number is added to all depths measured by the 491 so they will refer to depth from the surface, not from the transducer. This value should have been set correctly during installation and should not be changed. You can change the depth units to feet, meters, or fathoms: 1. Press the CURSOR PAD up or down to highlight the DEPTH UNITS option. 2. Press EDIT. 3. Press the CURSOR PAD left or right to highlight the desired units. Press ACCEPT.

3. At the GAIN window, press the CURSOR PAD left or right to adjust the gain, or use the KEYPAD to manually enter the desired gain value. The available settings range from zero (minimum) to 75 (maximum).
Gain window The window shows the effect of adjusting the gain. The fish symbols near the bottom of the window represent various echo strengths, and the expanding and contracting color bar above shows the colors that will be used to display these echoes. As you adjust the gain to obtain the best looking picture, also watch the real echoes on the right side of the screen. 4. Press RETURN to go back to the ECHO screen. When you adjust the gain, the color of the AUTO and PICTURE key tabs changes from green to yellow, since the echo sounder is no longer in automatic mode. Also, a yellow tab appears under the DEPTH key, indicating that the range setting is no longer automatically controlled and that the 491 may not always identify the bottom reliably.
Adjusting the clutter (weak echoes)
The clutter setting selects the echo strength that will be displayed using the bottom colors of the color bar (the weaker echoes). Any echoes weaker than this selection will not be 491 Echo Sounder Operations Manual Page 29
displayed. If you select 5, for example, all weak and moderate echoes will be displayed using the background color (just as if they werent there). You might choose this setting to eliminate high levels of background noise and echoes from turbulence or plankton. A setting of 0 allows all echoes to be displayed. To adjust the clutter: 1. At the ECHO screen, press PICTURE. 2. At the PICTURE screen, press CLUTTER. 3. Press the CURSOR PAD left or right to adjust the clutter, or use the KEYPAD to manually enter the desired clutter value. The available settings range from zero (minimum) to nine (maximum).
Clutter window 4. Press RETURN to go back to the ECHO screen. When you adjust the clutter, the color of the AUTO and PICTURE key tabs changes from green to yellow, since the echo sounder is no longer in fully automatic mode.
Adjusting the signal level (weak echoes)
As with the CLUTTER key, the SIGNAL LEVEL key controls the appearance of low level noise in the picture. Whereas clutter compresses or expands the available colors to fit the Page Echo Sounder Operations Manual

desired signal range, Signal Level completely removes the weaker colors and their echoes. To adjust the signal level: 1. On the ECHO screen, press PICTURE. 2. On the PICTURE screen, press SIGNAL LEVEL. 3. At the SIGNAL LEVEL window, press the CURSOR PAD up or down to remove the weaker color levels from the picture, or use the KEYPAD to manually enter the desired signal level. The available settings range from 1 (minimum) to 5 (maximum). For example, if you select a signal level of 3, echo strengths of 0 through 3 are all displayed using the same color. 4. Press RETURN to go back to the ECHO screen.
Suppressing interference (the noise limiter)
The noise limiter reduces the adverse effects of interference from other nearby echo sounders or electronic devices. however, the noise limiter may cause some very weak echoes to be made smaller or entirely eliminated, since it removes any echoes that arent sustained for at least two pings. To turn on the noise limiter: 1. At the ECHO screen, press PICTURE. 2. At the PICTURE screen, press NOISE LIMITER. 3. At the NOISE LIMITER window, press the CURSOR PAD up to turn the noise limiter on (or press NOISE LIMITER again). 4. Press the RETURN key to go back to the ECHO screen. Turning the noise limiter on changes a portion of the PICTURE key tab from green to yellow, as a reminder.

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Selecting the color bar (hue) and white level
Understanding the color bar
The color bar displayed at the extreme left of the ECHO screen shows the range of colors used to display different echo strengths. Weaker echoes are displayed with colors near the bottom of the scale, and stronger echoes are displayed with colors near the top. You can choose any one of nine palettes of colors to represent the echo strengths from weakest to strongest. Color bar #1 is the one most often used. Color bar #2 is similar but with fewer colors, to aid visibility under some conditions. Color bars # 3-8 are additional variations with different background colors. Color bar #9 uses only a single color, ranging from very dark to very bright.
Selecting the color bar (hue)
To select the color bar: 1. On the ECHO screen, press PICTURE. 2. Press HUE. 3. At the HUE AND WHITE LEVEL window, press the CURSOR PAD left or right to select the color bar desired, or use the KEYPAD to manually enter the number of the color bar.

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Hue and white level window 4. Press RETURN to go back to the ECHO screen.

Setting the white level

You can replace any single color in the color bar with white. On the HUE AND WHITE LEVEL window, press the CURSOR PAD up or down to select that color. To remove the white level and return to using all the colors on the color bar, press the CURSOR PAD down until the white level moves off the color bar.

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When you use the position marker on a split screen (showing either two frequencies, or zoom mode), each half of the screen has a position marker. Both markers designate the same physical location.

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Echoes from the last 3000 pings are stored. The number of minutes of past echo data available depends on two factors: the depth of the water the advance speed
In deeper water, the 491 pings at a slower rate, so the echo sounder saves data over a longer period of time. A slower advance speed will have the same effect.

Marking sh as waypoints

The 961/962s fish marking function lets you use SoundTrac to mark fish, wrecks, or any other objects that you see at any past echo displayed on the screen. To mark echoes as waypoints: 1. At the ECHO screen, press the CURSOR PAD to the left to move the position markera dashed vertical lineto the position of the echo. 2. Press MARK. A *MARK##* waypoint immediately appears on the SOUNDTRAC screen and on the CHART screen. Each marked echo becomes a waypoint (named *MARK##*) stored in the waypoint database. You can perform all of the usual waypoint functions, including going directly to this waypoint, adding it to the end of your trip, changing its name, etc.
Navigating to a past echo position
On the SOUNDTRAC screen, the GO TO function can be used for any of the following functions: to go directly to a past echo position to add a past echo position to the end of your trip to store a past echo position as a waypoint or avoidance point to make a new route with a past echo position as its rst waypoint Page 53
to add a past echo position to the end of an already displayed route
Going to a past echo position is described below. The other options are described in the Operators manuals for your Northstar navigator.
Going directly to a past echo position
To go directly to a past echo position (as long as the GPS is providing position data): 1. On the SOUNDTRAC screen, press the CURSOR PAD left or right to move the position marker to the desired position, then press GO TO. The SELECTED CURSOR POSITION window appears. 2. Press GO NOW. The navigator creates a new temporary waypoint called COORD and returns to the SOUNDTRAC screen. The COORD waypoint isnt stored in the waypoint database; instead, its placed in the trip, where it replaces any future trip points. To see this current waypoint on the CHART screen, press CHART at any time. Your present vessel position and time have now become a past trip point.

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Setting the Alarms
Understanding the alarms. 7-56 Setting the fish alarm. 7-56 Setting the bottom alarm. 7-58 Setting the temperature alarm. 7-60
This chapterfish, bottom, and temperature three alarm the describes the echo sounders functions (for conditions):
settings for each alarm, and how to turn them on and off.

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Understanding the alarms
The echo sounders alarms work just like the other alarms. Their status is updated every second, and their messages are displayed in the following ways: at the bottom of the ECHO screen, and also on various windows that may be overlaid onto these screens on the ALARMS screen
On this screen, you can manually clear, or stop, new alarms, although some are auto-clearing, and you can view old alarms, which are alarms that already have cleared.
To alert you automatically in situations related to echo sounding, you can set three alarms: sh alarm seabed bottom alarm temperature alarm NOTE:
You also can set the echo sounder to automatically save *FISH##* or *THERM##* waypoints, when fish or a certain temperature are detected, if the fish or temperature alarms are on. To automatically save these waypoints, see Number of special waypoints starting on page 2-14.

Setting the sh alarm

When the fish alarm is on, an alarm sounds if an echo returns from either inside or outside specific upper and lower limits youve set. To set the fish alarm: 1. At the ECHO screen, press MORE. 2. Press ALARM. 3. At the ALARM screen, press FISH ALARM. The options on the FISH ALARM window are on/off, echo strength level, upper and lower marker depths, and inside or outside markers.

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4. Follow the instructions below for each of these ve settings.

Fish alarm window

Setting the alarms echo strength level
To set the fish alarms minimum echo-strength level: 1. At the FISH ALARM window, press SET ALARM LEVEL. 2. Press the CURSOR PAD up and down to set the echo strength level from 1 to 15, as represented on the vertical color bar. Echoes received that are strong enough to be within the crosshatched area on the vertical bar will cause an alarm (weaker echoes will be ignored).
Setting the upper and lower marker depths
The fish alarm will sound only when there are echoes inside (or optionally, outside) the upper and lower markers. These markers are displayed on the ECHO screens. To set the depth of the upper marker: 1. At the FISH ALARM window, press SET UPPER MKR. The upper marker window is highlighted in black.

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2. Press the CURSOR PAD up or down to set the depth, or use the KEYPAD to manually enter the desired depth. The depth is displayed in the tab below the SET UPPER MKR key. To set the depth of the lower marker: 1. At the FISH ALARM window, press SET LOWER MKR. The lower marker window is highlighted in black. 2. Press the CURSOR PAD up or down to set the depth, or use the KEYPAD to manually enter the desired depth. The depth is displayed in the tab below the SET LOWER MKR key.

Setting inside or outside sh markers
If you designate the markers as inside markers, the fish alarm sounds when fish are detected within these markers. If you set these markers as outside markers, the fish alarm sounds when fish are detected outside of these markers. To set the markers to inside or outside, at the FISH ALARM window, press INSIDE/OUTSIDE MKRS to toggle between the inside and outside settings. The setting is displayed in the tab below the INSIDE/OUTSIDE MKRS key.
Turning the sh alarm on and off
To turn the alarm on, at the FISH ALARM window, press TURN ALARM ON. Generally, youll want to turn the alarm on after making all the other settings. To turn the alarm off, press TURN ALARM OFF.

The alarm

When fish are detected, the alert tone sounds and the message FISH! is displayed. This message clears automatically after 20 seconds and the alarm is rearmed.

Setting the bottom alarm

When the bottom alarm is set, an alarm sounds if the echo sounder detects that the bottom is shallower than the limit youve set.

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To set the bottom alarm: 1. At the ECHO screen, press MORE. 2. Press ALARM. 3. At the ALARM screen, press BOTTOM ALARM. The options on the BOTTOM ALARM window are on/off and the depth setting.

Bottom alarm window

Setting the bottom level
You can set the depth level for the seabed, so that as soon as the bottom is shallower than this depth, the bottom alarm will sound. To set the bottom level, at the BOTTOM ALARM window, press the CURSOR PAD up or down to set the depth, or use the KEYPAD to manually enter the desired depth. NOTE:
The 491s depth indicator reflects the depth below your vessels transducer, not below the keel. Ask your installer for the exact distance between your transducer and your keel. This value must then always be manually added to the 491s depth indicator, or else entered into the transducers depth setting on the ECHO SOUNDER SETUP screen for an automatically correct reading.

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Turning the bottom alarm on and off The alarm

To turn the alarm on, at the BOTTOM ALARM window, press TURN ALARM ON. To turn the alarm off, press TURN ALARM OFF. When the bottom is detected, the alert tone sounds and the message Bottom Collision! is displayed. This message clears automatically after 20 seconds, and the alarm is reset.
Setting the temperature alarm
This alarm isnt present unless a temperature sensor is installed and configured.
When the temperature alarm is set, an alarm sounds if the echo sounder detects that the water temperature has either risen above or dropped below the limit youve set. To set the temperature alarm: 1. At the ECHO screen, press MORE. 2. Press ALARM. 3. At the ALARM screen, press TEMP ALARM. The options on the TEMPERATURE ALARM window are on/off, upper and lower limits, and inside or outside limits.

Temperature alarm window

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Setting the upper and lower temperature limits
You can set the upper and lower temperature limits. When the water temperature is either inside or outside these limits, the temperature alarm will sound. To set the upper temperature limit: 1. At the TEMPERATURE ALARM window, press SET UPPER LIMIT. The upper limit window is highlighted in black. 2. Press the CURSOR PAD up or down to set the temperature, or use the KEYPAD to manually enter the desired temperature. The temperature is displayed in the tab just below the SET UPPER LIMIT key. To set the lower temperature limit: 1. At the TEMPERATURE ALARM window, press SET LOWER LIMIT. The lower limit window is highlighted in black. 2. Press the CURSOR PAD up or down to set the temperature, or use the KEYPAD to enter the desired temperature. The temperature is displayed in the tab just below the SET LOWER LIMIT key.
Setting inside or outside temperature limits
If you set the upper and lower temperature limits as inside limits, the temperature alarm sounds when the temperature is detected within these limits. If you set these limits as outside limits, the temperature alarm sounds when the temperature is detected outside of these limits. Press INSIDE/OUTSIDE LIMITS on the TEMPERATURE ALARM window to switch between the inside and outside settings. The current setting is displayed in the tab just below the INSIDE/ OUTSIDE LIMITS key.
Turning the temperature alarm on and off
To turn the alarm on, at the TEMPERATURE ALARM window, press TURN ALARM ON. To turn the alarm off, press TURN ALARM OFF.

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When the temperature alarm sounds, an alert message is displayed. This message clears automatically after 20 seconds and the alarm is reset.

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Troubleshooting 491 Operations
Troubleshooting the echo sounder. 8-64 Checking the transducer. 8-65
This chapter returninghow to troubleshootfactory service. explains the echo sounder system before the equipment for

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Troubleshooting the echo sounder
No echoes displayed when STAR key is pressed.

Is the Advance Speed set to zero?
Change the Advance Speed setting.
Contact Northstar Service to upgrade to the latest version of 961/962 software.
Is the 961/962 software Version 3.0 or greater?
Configure NMEA Port 3 for the 491. See Section 1 of this manual for instructions.
Has NMEA Port 3 been configured for the 491?
YES 491 is communicating with the navigator Check the 491's STAT indicator STEADY GREEN 1. Check transducer connector for the proper wiring. 2. If wiring is correct,check transducer impedance with an ohmmeter. 3. If the transducer is open or shorted, replace it
1. Check fuses and circuit breakers 2. Check power to 491 with a voltmeter. 3. Verify that the data cable between the 961/962 and the 491 is properly wired and connected.
FLASHING GREEN The 491 and the 961/962 aren't communicating properly. Check the wiring of the data cable between the 961/962 and the 491.
There's a hardware problem with the 491.
Figure 9: Troubleshooting the echo sounder (961/962)

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No echoes displayed on sounder screen.
Configure the navigators Aux Port for the 491. See Section 1 of this manual for instructions.
Has the navigators Aux Port been configured for the 491? YES 491 is communicating with the navigator.
1. Check fuses and circuit breakers. 2. Check power to 491 with a voltmeter. 3. Verify that the data cable between the navigator and the 491 is properly wired and connected.
Check the 491's STAT indicator

STEADY GREEN

FLASHING GREEN The 491 and the navigator aren't communicating properly. Check the wiring of the data cable between the navigator and the 491.
1. Check transducer connector for the proper wiring. 2. If wiring is correct,check transducer impedance with an ohmmeter. 3. If the transducer is open or shorted, replace it
Figure 10: Troubleshooting the echo sounder (957/958)

Checking the transducer

To provide the best possible performance with the 491 echo sounder, Northstar recommends the use of an Airmar

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transducer. The models below can be purchased from Northstar.

Table 3: Northstar-recommended transducers

Manufacturer

Airmar Airmar Airmar
B260 B744V (w/3-wire speed) P66

1 kW 600 W 600 W

Northstar P/N

TD1004 TD1005 TD1006

Airmar Technology Corporation may be reached at 35 Meadowbrook Drive, Milford, New Hampshire 03055-4613; phone 603/673-9570; fax 603/673-4624. NOTE:
Detailed information on maintaining and troubleshooting a transducer is outside the scope of this manual. Refer to the transducer manufacturers documentation. Do not return a transducer to Northstar. If you need to return a transducer for service, contact the manufacturer directly for instructions.

Maintaining a transducer

Do not expose a transducer to gasoline or clean it with strong solvents. These can penetrate and degrade the housing. If a transducer will be exposed to saltwater, coat it with anti-fouling paint to prevent sea growth. To clean a transducer of sand, debris, or sea growth, use a stiff brush or putty knife. Use sanding sparingly, as repeated sanding may affect a transducers performance at high speeds. If necessary, wet sand with finer grade wet or dry paper. Check the transducer periodically.

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491 Features and Specications
Table 4: 491 echo sounder features
Performance characteristics
Output Alarms Update rate Auto modes Zoom modes Features Single/Dual Channel, 50/200kHz, 600W Fish, seabed, temperature 10 Hz maximum (depends on water depth) Fishing and cruising Marker, bottom, bottom lock, bottom lock/center Mark present or past echo as waypoint (961/962) Go directly to any past echo A-scope analyzes present or past echoes Navigation data shown at bottom of screen Demo mode for training

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Table 4: 491 echo sounder features (Continued)

Screen notations

Echo data Seabed depth (various size digits) Frequency of each window Speed through water (if connected) Water temperature (if connected) Depth scale for each window Depth of depth marker Latitude/longitude of position marker and vessel Alarm status and auto/manual status Zoom mode Name of waypoint, and distance and bearing to waypoint Steering indicator

Interfacing

Connects Northstar 961/962 GPS Chart Navigator Northstar 957/958/6000i GPS Chart Navigator Northstar-recommended or compatible transducer Transducer outputs protected against open circuit/ short circuit LED monitors input power and system status

Physical characteristics

Dimensions Weight 8.78 x 7.22 x 2.35 inches 2 pounds
Environmental characteristics
Temperature Protection Standards -25C to +60C operating temperature -55C to +90C storage temperature 8 to 36 VDC, 8 Watts, reverse polarity and overvoltage protection Waterproof design meets the following: IEC60529 IP6; IEC60945 emissions; CE mark