Thanks all, I'll just bite the bullet and buy new. I had been debating if I could get by with a 12 volt motor - which appears to max out at 55lb thrust, and I wanted to see how one of similar size might move my boat.
But I'm convinced I need to go with 24 volt 70lb minimum thrust.
I don't plan on taking my boat out fishing again until spring so I'm not in any rush.
Thanks again for the willing generous offers.