Similar to another thread, I am having the same issue, for the last 6 years, in that everyone, including Hummingbird and other professional techs, keep telling me that my transducer is mounted in the correct spot, yet anything between idle and WOT give me readings in the hundreds of feet, and tons of fish, even if I am in 4'-16+' of water. It is very frustrating as this unit has never worked right since it was installed. I have changed transducers twice and even the head unit once.
I think it has something to do with having a jackplate and possible cavitation issues that presents, but they have all said that isn't the issue. I dont want to move it, again, just yet, as if I end up keeping the boat, I will want to put trim tabs on it and then that could open up another can of worms.
I have played with every setting to try and get it to work and changed the tilt on the transducer. Nothing seems to help.