Recently my trolling motor took a dump on me while at the lake. It was running fine and we were using it to get back to the dock after having engine trouble when it suddenly just died. We paddled back. Later I was looking at it and it seemed that the prop shaft was bent slightly so I figured I must have damaged it somehow, maybe hitting a stump or getting caught up in underwater tangles. When the boat mechanic fixed the engine he also said I must have bent it as well so I was sure that was it. The thing would only turn 1/2 a turn and then just hang up and the motor would hum. This also helped convince me that it was just bent.

I ordered a new armature for it since this is the prop shaft, the entire thing is one piece, coils and all. I also ordered new seals, and when it came in I installed it all. Now after doing this, I still have the same problem so apparently this wasn't it. Motor still turns 1/2 a turn and stops and hums. What else is there? I know there is a circuit board inside the body of the motor that mounts on the deck, right where the power cord comes out, right where the battery life meter is at also. Everything else on the motor works, the electronic steering and the battery meter. That's about all there is to it other than the motor itself. As near as I can tell, the brushes still look good too. There is a lot of material left on them anyway. Could it be possible to lose power to just one of them and have this happen? That could be just a simple wiring problem then.

Did you check the magnets that are glued to the inside wall of the housing? sounds as if one of them has come loose.

There are none that I can see. It's an empty cylinder with two slots cut end to end to allow the long fastening screws to go through along side of the armature. It's highly magnetic though. I have to hold the armature down hard while reassembling everything or it will try to center itself in the cylinder, which is incorrect, and it pulls away from the brushes.

Since it is magnetic, I know that impacts can depolarize a magnet, which effectively demagnetizes it. Could this have happened? I have hit stumps with it, but it was running fine in open water later on. That's what makes me think some electronic component has failed. If so then it must be in the body of the motor that attaches to the deck of the boat. Foot pedal works fine and the armature is new. Is it possible to use a VOM on the brushes to check for voltage there?