I had the same issue when my father-in-law (the electrian) helped me install my new troller motor. The motor did not work when I plugged it into the socket. The boat is setup for a 12/24. It was a good thing the in-law was there. He changed the wires at the plug and it has worked just fine since then. Sorry I cant give you more information, but the change is in the plug. He toke the cover off the plug and changed the wire setup. This was one of the new 24 volt Moter Guide motors.
Hope this Helps