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Fishfinder 250/250C Owner’s Manual
11
Shoot-Thru-Hull Installation
To avoid drilling a hole to mount a thru-hull transducer, a transducer
may be secured with epoxy inside a boat (“shoot-thru-hull”
installation). This type of installation can reduce noise 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. If you are unsure of your boat type, contact the
manufacturer. Professional installation may be necessary. Always
wear a dust mask and safety goggles when installing.
Some transducers are specifically designed to be mounted inside a
fiberglass hull. The standard plastic transom mount transducer can
also be mounted in this fashion using the following method. If using
a temperature sensing transducer, the temperature displayed reflects
the hull temperature.
When choosing a location for the transducer, consider the following
conditions:
• The location has to be solid fiberglass, devoid of any air
bubbles, laminates, fillers, or dead air space.
• The location needs to be in an area of clean 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.
NOTE:
Many modern hulls have a prelocated 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 below.
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 liquid, pointed directly at
the bottom. Weight it down. Set the unit for optimum
performance. If the sonar performance is significantly
degraded, find and test another location.
Testing the Location
Strip Caulk
or RTV Sealer
Hull
PVC Pipe
or a Can
Weight transducer
to hold it in place
Fill pipe or can
with water or a
light mineral oil
