Minn Kota electric motor troubleshootin?

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I've got a 24 v bow mount foot-control Minn Kota trolling motor that is acting up and has since I got it (used). I've never been able to run it at 100% it shuts off, turns on for a second, then turns off. So I've found if I run it at 50% I have no issues, so that's what I've done the last few seasons. But I'd like to fix the issue once and for all. I'm running a 50 amp fuse and thick gauge wired. Any suggestions? The + wire seems to get hot coming from the battery when it's running.
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