Garmin Fishfinder 340C Owner's Manual page 19

Shoot-Thru-Hull Installation
To avoid drilling a hole to mount a thru-hull transducer, a
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. Be sure to always wear a dust mask and safety goggles.
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 shown reflects the hull temperature.
Selecting a Location for a Shoot-Thru-Hull Installation
When installing a transducer, the installation location must be the
following:
• Solid fiberglass, without any air bubbles, laminates, fillers, or
dead air space.
• 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 at speed.
Fishfinder 340C Owner's Manual
I F
NSTALLING THE ISHFINDER
NOTE: Many modern hulls have a dedicated pocket for
shoot-thru-hull transducer installation. If you are unsure if 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 with water or light mineral oil.
3. Place the transducer in the water, pointed directly at
the bottom and weight it down. Set the unit for optimum
performance. If the sonar performance is significantly
degraded, another location must be tested.
PVC pipe
or a can
Strip caulk
or RTV sealer
Hull surface
Testing the Location
340C > M T
OUNTING THE RANSDUCER
Weight the transducer to
hold it in place.
Fill a pipe or can with water
or a light mineral oil.
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