Eagle Fishmark 320

Can anybody tell me why my fishmark 320 screen scrolls along at the same
rate no matter how fast or slow I am going, and even when I am anchored? I
was anchored in my 36' pond prowler (that's sq. ft) and the screen is just
scrolling along at the same pace as when I was trolling. The fish are
showing up moving along also, all in the same relationship to each other. I
don't think they are all drifting with the current, but I suppose that's
possible. And, no, I don't have it on simulator.

Thanks.
Keith