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GPSMAP 400/500 Series Installation Instructions 

Installing a Transducer

Consult the chartplotter feature matrix on 

page 1

 to determine if your chartplotter is capable of using sonar. The following transducer 

installation procedures are only applicable to sonar-capable chartplotters. 

NOTE

: The following procedures contain installation instructions for the transducer included with the “s” model GPSMAP 400/500 series 

chartplotters. If you choose to use a different transducer, installation instructions are provided in the transducer kits. Some transducers might 

have to be installed by a professional marine installer.

Proper transducer installation is key to getting the best performance from your sonar-capable chartplotter. Be sure you have the following 

components in the transducer package, as well as the following tools:

Transducer Package

•  Transom-mount transducer (not pictured)

A  – 5 mm flat washers (2)

B  – 5 

×

 30 mm screws (2)

C  – 10-32 lock nut (1)
D  – 4 

×

 12 mm screw (4)

E  – 10-32 

×

 1.75 in. screw (1)

F  – 

1

/

4

 in. cable clamps (2)

G  – Plastic spacer (1)
H  – 

1

/

4

 in. rubber washer (1)

I  – Cable tie, 5.6 in. (4)
J  – Cable entry cover (1)

F

H

C

D

I

J

G

E

A

B

Tools Needed

•  Drill and drill bits
• 

3

/

8

 in. (9.5 mm) wrench or socket

•  Masking tape
•  Number 2 Phillips screwdriver
•  Marine sealant

 

NotIce: 

Do not cut the transducer lead or any part of the transducer cable. Cutting the transducer cable voids your warranty. The cable cannot be 

spliced and connected to any existing (Garmin or non-Garmin) transducer cables. If the transducer lead is too short, extension cables are available from 

your Garmin dealer.

Assembling the Transducer

1.  Insert the rubber washer (H) and the plastic spacer (G) into the transducer 

at the same time. DO NOT lubricate the rubber washer.

2.  Route the power/data cable toward the back of the transducer. Slide the 

transducer into the transducer mount.

3.  Place a 5 mm flat washer (A) on the 10-32 × 1.75 in. screw (E), and insert 

the screw through the transducer mount, the spacer, and the rubber 

washer.

4.  Place the remaining 5 mm flat washer (A) on the exposed end of the 10-32 

× 1.75 in. screw. Install the 10-32 locknut (C) finger tight. Retighten the 

transducer after installation on the boat.

Mounting the Transducer on a Transom

When selecting a transom-mount location, consider the following for optimal performance:

For your sonar to operate properly, the transducer must be located in calm water.
Mount the transducer as close to the center of the boat as possible.
Do not mount the transducer in locations where it might be jarred when launching, hauling, or storing.
Do not mount the transducer in the path of the propeller on single-drive boats. The transducer can cause cavitation that can degrade the 

performance of the boat and damage the propeller. On twin-drive boats, mount the transducer between the drives, if possible.

Note:

 Do not mount the transducer behind strakes, struts, fittings, water intake or discharge ports, or anything that creates air bubbles or 

causes the water to become turbulent. The transducer must be in clean (non-turbulent) water for optimal performance.




Back of the transducer

Cable tie slot

E

G

H

A

C

Back of the transducer

Cable tie slot

E

G

H

A

C

Summary of Contents for GPSMAP 420

Page 1: ...ing always check the opposite side of the drilling or cutting surface To install and use your chartplotter 1 Select a mounting location page 2 2 Mount the chartplotter page 2 3 Install the transducer...

Page 2: ...unting the Chartplotter Use the included bracket to surface mount the chartplotter You will need the following tools and fasteners Drill Phillips or flat screwdriver Three 8 4 mm pan head machine bolt...

Page 3: ...If the transducer lead is too short extension cables are available from your Garmin dealer Assembling the Transducer 1 Insert the rubber washer H and the plastic spacer G into the transducer at the sa...

Page 4: ...distance between the transducer and the top of the transom 6 Mark the location Drill a 1 8 in 3 2 mm pilot hole approximately 3 8 in 9 5 mm deep 7 Attach the cable clamp using one of the 4 12 mm scre...

Page 5: ...GPSMAP 525 535 545 555 526 536 546 556 or with non s models compatible with a GSD 22 When installing a transducer consider the following The hull must be composed of solid fiberglass without air bubb...

Page 6: ...ss Do not cut the transducer cable because this voids your warranty Notice The maximum input voltage is 32 Vdc Do not exceed this voltage because this can damage the chartplotter and void the warranty...

Page 7: ...ce 3 Repeat step 2 using the grey and violet wires for an additional NMEA 0183 device 4 Set the serial port s on the chartplotter to use NMEA 0183 data standard or high speed See the GPSMAP 400 500 Se...

Page 8: ...n existing NMEA 2000 network on your boat you will need to build one See www garmin com for more information NOTE NMEA 2000 compatible GPSMAP 400 500 series chartplotters are not packaged with NMEA 20...

Page 9: ...6 GPSMAP 420 430 431 440 and 450 GPSMAP 430x and 440x GPSMAP 421 441 and 451 GPSMAP 521 541 551 GPSMAP 530 535 540 and 545 Testing the Installation To turn on your chartplotter for the first time pres...

Page 10: ...l 12 7 cm Full VGA display with adjustable brightness 640 480 pixels capable of 4 096 colors Case Fully gasketed high impact plastic alloy waterproof to IEC 529 IPX7 standards Temp Range From 5 F to 1...

Page 11: ...roduct Information 126996 Product Information 127250 Vessel Heading 127250 Water Depth 127488 Engine Parameters Rapid Update 128259 Speed Water Referenced 127489 Engine Parameters Dynamic 128267 Water...

Page 12: ...py of this manual or of any revision hereto provided that such electronic or printed copy of this manual must contain the complete text of this copyright notice and provided further that any unauthori...

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