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4  

GPSMAP 400/500 Series Installation Instructions

To mount the transducer on a transom:

1.  Position the transducer mount at the selected transom location. Make sure the transducer is parallel with the water line. Mark the center 

locations of each hole on the transducer mount.

Apply marine sealant to all screw 

threads to prevent water from 

seeping into the transom.

Mount the transducer 

cable cover far above 

the waterline.

The transducer should 

extend 

1

/

8

 in. (. mm) 

below a fiberglass hull or 

3

/

8

 in. (9.5 mm) below an 

aluminum hull.

Ensure that the transducer is 

below water level when the boat 

is on plane at high speed.

Do not mount the transducer directly in the path of the 

propeller. The transducer can cause cavitation that may 

degrade the boat performance and damage the propeller.

Mount the transducer parallel 

with the bottom.

2.  Drill 

5

/

32

 in. (4 mm) pilot holes approximately 1 in. (25 mm) deep at the marked locations. To avoid drilling the holes too deep, wrap a piece of 

tape around the bit at 1 in. (25 mm) from the point of the bit. 

3.  Apply marine sealant to the 5 × 30 mm screws (B). Attach the transducer assembly to the transom using the 5 × 30 mm screws. Adjust the 

transducer assembly to extend beyond the bottom of the transom approximately 

1

/

8

 in. (3.2 mm) on fiberglass hulls or 

3

/

in. (9.5 mm) on 

aluminum hulls. Adjust the transducer assembly to be aligned parallel with the bottom.

4.  Tighten the 10-32 locking nut until it touches the mounting bracket, and then tighten 

1

/

turn more. (Do not overtighten.)

5.  Place the first cable clamp (F) on the transducer cable, approximately one third of the distance between the transducer and the top of the 

transom. 

6.  Mark the location. Drill a 

1

/

in. (3.2 mm) pilot hole approximately 

3

/

in. (9.5 mm) deep.

7.  Attach the cable clamp using one of the 4 × 12 mm screws (D). Coat the screw with marine sealant before installation. Repeat steps 5 and 6 

using the other cable clamp. 

8.  Route the transducer cable to the GPSMAP 400/500 series chartplotter.

 

NotIce: 

Avoid routing the cable close to electrical wires or other sources of electrical interference.

9.  Test the transducer installation after you complete the GPSMAP 400/500 series chartplotter installation. See 

page 9

.

Mounting a Transducer on a Trolling Motor

1.  With the ridges of the band facing up, slide the large cable tie through the slot on the transducer mount until equal lengths extend on both 

sides of the mount. 

 

NotIce: 

For cold water and heavy timber or debris areas, a metal 4-5 in. (100-125 mm) worm gear clamp is recommended instead of the plastic  

cable tie.

2.  Position the mount gasket on the curved top of the transducer mount.
3.  With the front of the transducer pointed away from the trolling motor propeller, place the transducer 

assembly against the motor body of the trolling motor.

4.  Wrap the two ends of the cable tie around the motor body. Place the pointed end of the cable tie through 

the fastener hole on the opposite end and pull it through until it is snug but not tight. (The cable tie clicks 

when you pull it.)

5.  Position the transducer so that it is parallel with the bottom when in use, making sure the gasket is 

aligned properly. Pull the cable tie end until tight. Trim off the excess if necessary. Tighten the locking nut 

until it touches the mounting bracket, and then tighten 

1

/

4

 turn more. (Do not overtighten.)

Cable tie

Front of the transducer

Cable tie

Front of the transducer

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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