Started getting some weird readings on my HB 898c hd si. Depth reading will go crazy even in deep water. Sometimes it will continually flash the sane depth for several minutes, Standard sonar will be fine and then lose all detail, pretty much turning white, with some light green streaks. SI and Down image not affected. Is it the depth finder or the transducer? I don't know anyone with an 898 I can borrow. Best guess?