Garmin Fishfinder 250 Owner's Manual

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GETTING STARTED > INSTALLATIONFishfinder 250/250C Owner’s Manual 11Shoot-Thru-Hull InstallationTo avoid drilling a hole to mount a thru-hull transducer, a transducermay be secured with epoxy inside a boat (“shoot-thru-hull”installation). This type of installation can reduce noise and allow youto use a higher gain setting. For a transducer to be mounted insidethe hull (shoot-thru, not thru-hull), the boat must be fiberglass,with no core. If you are unsure of your boat type, contact themanufacturer. Professional installation may be necessary. Alwayswear a dust mask and safety goggles when installing.Some transducers are specifically designed to be mounted inside afiberglass hull. The standard plastic transom mount transducer canalso be mounted in this fashion using the following method. If usinga temperature sensing transducer, the temperature displayed reflectsthe hull temperature.When choosing a location for the transducer, consider the followingconditions:• The location has to be solid fiberglass, devoid of any airbubbles, laminates, fillers, or dead air space.• The location needs to be in an area of clean water at allspeeds.• The location must not be over any strakes or behind anyobstruction on the hull that would create turbulence at speed.NOTE: Many modern hulls have a prelocated pocket forshoot-thru-hull transducer installation. If you are unsure if yourhull is equipped with a pre-located pocket, contact your hullmanufacturer.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 orRTV sealer, and fill with water or light mineral oil.3. Place the transducer in the liquid, pointed directly atthe bottom. Weight it down. Set the unit for optimumperformance. If the sonar performance is significantlydegraded, find and test another location.Testing the LocationStrip Caulkor RTV SealerHullPVC Pipeor a CanWeight transducerto hold it in placeFill pipe or canwith water or alight mineral oil