I'm having trouble getting my new Garmin Fishfinder 140 to work properly. It came with a transom mount transducer which I siliconed to the center of the lowest plank in the aft port cabin locker (a good place I thought). When I do get a reading, it seems to be accurate as measured against a handheld depth meter and other boats, but the problem is I don't always get a reading (just shows zero indefinitely) or I initially get a reading which doesn't change as the water depth changes. On the Chesapeake Bay Cruise I used it for more than a few hours and it either read zero for long periods or read accurately for only a short time. I finally gave up on it. Today I popped it off. The silicone seal seemed tight with no air gaps. I went to the river and while using silly putty I couldn't get any reading (other than zero) from it, trying 6 or 7 different spots. I put it over the side with the silly putty still on the transducer and got no reading. I cleaned the putty off and put it over the side and got accurate readings once it started to register. Registering took from 10 seconds to sometimes minutes and a few times never showed anything but zero after being on many minutes. Before I go to Garmin, who will probably tell me I ruined the transducer trying to silicone it to the floor, I thought I'd pass it by you smart folks. Thanks, Rick Langer M15 #337 Bluebird