It is a bad transducer. Marcum was purchased by nature vision. Give customer service a call at 866-777-0733 and they will help you out. I have not delt with them since the take over but from what I have heard they have been taking care of people. Please let us know how it turns out.
Even eminent chartered accountants are known, in their capacity as fishermen, blissfully to ignore differences between seven and ten inches, half a pound and two pounds, three fish and a dozen fish. ~ William Sherwood Fox, Silken Lines and Silver Hooks, 1954