I switched lower unit on my motorguide trolling motor with another I had sitting around. It went great but I found it had drained the batteries so I ended up doing more work on these motors than I had to and I would like to share what I learned since there isn’t much on the web.
The motor developed a wobble that was pretty bad on low speeds. I heard talk about bearings could be the problem on the web, so as long as I wasn’t using the lower unit anymore I figured I would take it apart and see if I could just switch bearings with the other head I had installed. There are no bearings, people just don’t want you knowing that. There are two brass bushings in the front and back that the armature shaft sits in. I removed the armature completely and noticed a spot that had worn down on the shaft. The only way to fix it would be to replace the armature which can cost about half the price of a new trolling motor.
If you hear a noise, it isn’t a bad bearing. There are two spring loaded connectors (don’t know what they are called) on the armature that wear out and they are easy and inexpensive to replace. I bought a grinder recently and it came with extra, so I know these wear out. I don’t know what they are called off hand and it is hard to find information on the web. I say easy to fix but everything has to be taken apart on the trolling motor, which isn’t real easy but it also isn’t real high tech.