Shoot-Thru-Hull Installation - Garmin GPSMAP 420 Installation Instructions Manual

6. Route the transducer cable to the GPSMAP 400/500 series chartplotter using cable ties to secure the cable to the motor shaft. You can fill
the forward-facing portion (except the cable tie pocket) of the transducer mount with sealant to avoid accumulating debris.
NotIce: Leave some slack in the cable to avoid damage while using the trolling motor.
NotIce: Avoid routing the cable close to electrical wires or other sources of electrical interference.

Shoot-Thru-Hull Installation

To avoid drilling a hole to mount a thru-hull transducer, a transom-mount transducer can be secured with epoxy inside a boat (shoot-thru-hull
installation). This type of installation can provide better noise reduction and allow you to use a higher gain setting. For a transducer to be
mounted inside the hull (shoot-thru, not thru-hull), the boat must be fiberglass with no core. Contact your boat manufacturer if you are unsure.
Professional installation might be necessary.
Some transducers are specifically designed to be mounted inside a fiberglass hull. The standard plastic transom-mount transducer can also be
mounted using this method. If using a temperature-sensing transducer, the temperature displayed reflects the hull temperature.
NOTE: A solid fiberglass hull can be no more than
thick when using a 1 kW transducer. 1 kW transducers are only compatible with either the 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 bubbles, laminates, fillers, or dead air space.
• The location must be in an area of clean (non-turbulent) water at all speeds.
• The location must not be over any strakes or behind any obstruction on the hull that would create turbulence.
NOTE: Many modern hulls have a dedicated pocket for shoot-thru-hull transducer installation. If you are unsure whether your hull is equipped
with a pre-located pocket, contact your hull manufacturer.
To test the location:
1. Fabricate a test device from a section of PVC pipe or a can, as shown in the following illustration.
2. Temporarily seal the test device to the hull with caulking or RTV sealer, and fill the test device with water or light mineral oil.
3. Place the transducer in the water, pointed directly at the bottom, weighted down. Set the device for optimum performance. If the sonar
performance is significantly degraded, another location must be tested.
To permanently install the transducer:
1. Lightly sand the surface of the hull and the face of the transducer with 400-grit wet or dry sandpaper.
2. Build a dam using strip caulk about
3. Place the transducer in the epoxy, turning the transducer to work out any air bubbles.
4. Weight the transducer in place, and allow it to cure for 24 hours.
GPSMAP 400/500 Series Installation Instructions
/ in. (9.53 mm) thick when using a 500 W transducer, and no more than 1 in. (25.4 mm)
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Strip caulk or
RTV sealer
Hull surface
Testing the Location
/ in. (6 mm) tall. Pour about
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4
Weight the transducer
PVC pipe to hold it in place.
or a can
Fill a pipe or a can with
water or a light mineral oil.
/ in. (3 mm) of two-part, slow-cure epoxy into the dam.
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8
5