Sounds like the transducer to me Downwind. If you have it mounted inside-the-hull than it could possibly be that the installation went bad but if it’s mounted on the transom than it is the transducer itself. You could check for damage to the transducer cable but I would just call the Humminbird Customer Resource folks at 1-800-633-1468 and see if they will just send you a replacement. That way you could run the cable for the new one over the transom and across the deck just to test it. If it all works than I would cut the cable on the one you have installed now and use it to pull the new one through (or a string which would be used to pull the new one through).