chuckd333

I have a Garmin 178c with an thru hull transducer. Not a shoot thru the hull but a real thru hull. I have it mounted in a 20ft Gatortrax aluminum boat. It is in the rear of the boat in the center. It looses bottom at about 5mph. It will not read at high speed unless I am making a turn. The turn can be in either direction and the transducer will start reading the bottom. I have physically cut another hole in my boat and moved it with the same results. Any Ideas??

Bullshipper

Sounds like you are getting bubbles sucked under the bow, that are traveling under the face of the transducer, interfering with the signal when you travel in a straight line, and that shift away from this location when turning.

Your options are these in my mind:
Find a turbulence free zone (deepest location on the hull near the transom where bubbles can escape before they reach this area, staying away from a strake that could be containing them).

Use some spacers to vertically lower the face below these bubbles in its current location (an 1/8 to 1/2" lower can make all the difference

Get or make a transom mount transducer that can be placed behind the transom in a location where you see the cleaneast water at high speed.

Hard to help more without being there.

dbcaster

Chuck,
Are you using a high speed fairing block? Is it a low profile transducer? As bullshipper said the transducer should be below the hull not flush with the bottom. You need to get below the bubbles that run along the hull. A high speed fairing block will lower the transducer.

warthog5

Need pix's of the bottom of the boat and transducer installed. We are gussing.
What may be obvius to us may not be to you.