2003 SCR 2400 My factory thru hull transducer is mounted forward of the engine almost to the gas tank. Only works in smooth water or idle. I had a Grady White WAC previously and epoxied (after grinding the hull smooth on the inside) inside the hull near the transom. Secret is to build a dam about slightly larger than the transducer by rolling play dough or plumbers putty in 1/4" dia pencil strips and mashing onto the hull. Flood with epoxy resin and gently push the transducer into the resin at a slight angle (prevents bubble formation) until it rests completely on the hull. Let it set 24 hours before hitting the water. Worked up to 200 feet. Never went out beyond that.