I had a Fortrex on my last boat and it did the same thing when turning while under power anytime over say 30%. There was also a creaking/popping noise when turning under power as well. There are a few threads over on BBC on the trolling motor forum, describing a solution for the popping noise, which is caused by the ball twisting inside the socket. As for the vibration, I adjusted the tension in the foot pedal, which helped, but didnt eliminate it. I have a motorguide on this boat, and I am much happier with operation if this one minus the lift assist that the Fortrex has.
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