I had a boat do this to me several years back and it was a spring inside the steering box behind the steering wheel. When yo turn the boat 1 way or anoter the spring would expand or contract. Over time the spring got rusty and failed and the boat would not hardly turn 1 way or another. It would just make a popping sound and be very difficult to turn the wheel like no power steering in a car. I went to the marine store and for $140 and a couple hours I fixed it myself with a new steering box. I just took the old part off and took it up there for a replacement. Make sure you route the cables the right way when I took the boat out I steered right and went left.

Shawn