My boat came with a Elite 5 HDI. The only two transducers I can select on it are 455 & 800. It hardly ever shows a fish. I bought a Garmin Striker 4 plus and it shows fish. It has a 77 or 200 transducer. Is the problem with the Elite 5 the transducer frequency? Can I just change the transducer to a 80/200 or am I stuck with the 455/800? It marks the bottom but never a fish.