I recently bought a used MK 65 Auto pilot trolling motor. When I set the AP it will track ok for a short time then trun alnost 180 deg. pretty quickly, like it's trying to keep me in one spot.
I've tried just punching the set button and holding it down for a couple of seconds. But it wants to do this either way. What am I doing wrong, or is there something wrong with the motor?

That happened to mine twice because the power plug was loose due to me fishing on the front deck and I musta stepped on the connector plug. Or check if your remote battery is not almost out. Also, when you deploy it, make sure the two (black) rings are fitted. My MK 65# AP came with my boat, used it for 1.5 yr and I like it alot but under power for my 21'8" CC especially the windy days, so I just upgraded to 101# Auto Pilot. Love it!