Hi Steely, did you get it fixed? I was having a crisis so it sounded more fraught than I meant it to. I actually have two working stern thruster motors in my garage, one propeller is toast but the motors worked when I took them off. Let me know if you need one, although with shipping it would probably be chaeper to rebuild yours...I still think the repair advice is valid. Probably a ground. If any of the cables terminate on stainless, like the grounds, that is probably the issue, notoriously difficult to get a good connection with stainless.
Don't believe everything that you think.