Trolling motor grind

[Arkman]

I got an older minnkota trolling motor from my grandpa and I have used it a bit and it works fine. The last time I used it it sounds like something inside is grinding a bit. Any thoughts on why, what to do to fix it?

Thanks!

 

[Silvertip]

Re: Trolling motor grind

Bad bearings or brushes going out perhaps. Spin the prop by hand to see if you can feel the grinding. Don't confuse that with the sort of pulsing feeling as those are the effects of the magnets in the motor. Roughness indicates an internal problem. Unless you have the tools and ability you might want to have a service center fix it. It could be the seals have worn and allowed water to get in the motor. Now that you are using it, the built up rust has begun to loosen and is dragging between the armature and magnets. Remove the prop and check for fish line wrapped around the shaft. This screws up lots of trolling motors as it cuts the seal allowing water into the motor.

 

[Arkman]

Re: Trolling motor grind

I did some looking. I took the prop off, didn't see anything but a small amount of weeds. I took that out and put the prop back on and turned it a little bit. Still grinding. I carefully took it apart a little farther and didn't see anything so I put it back together. Now I have to power to the motor. It will turn from the pedal but the prop wont turn. Any suggestions?

 

[Silvertip]

Re: Trolling motor grind

I have no idea what you mean when you said "I took it apart a little farther!" I expect you didn't assemble it correctly.

 

[Arkman]

Re: Trolling motor grind

Sorry for the lack of detail. My computer started freaking out and I couldn't type to much.

Anyways. The motor is made of 4 main parts. The prop, then a small section right behind the prop which has a bushing type thing that the shaft goes through, then the main section which is directly below the shaft (this part has the magnets and copper wire and stuff) then a back cap that has a little bushing thing that hold the back end of the shaft.

I took the the back cap off as well as slid the part right behind the prop off. I didn't disconnect anything or move anything inside. I did notice one of the magnets was broken in half. Its shaped like a C and it is broken right down the middle. I'm pretty sure this was like it before. I dont know how I could have broke the magnet.

Like I said, I didn't unhook anything (that I noticed) or move anything (again, that I noticed). I put it back together and then no spinning. The inside is fairly basic looking, and everything other then the magnet seem to be intact.

Does this make sense?

 

[Silvertip]

Re: Trolling motor grind

Did you disturb the brushes or allow them to pop out of their holders. How did the armature look? If you removed both bearing caps, the armature had to move and was likely sucked against the magnets. The grinding you hear when the motor did work was very likely debris from the broken magnet. There is very little space between the armature and magnet so anything that gets in that space will make it grind. You can look at the armature to see if there is any obvious marks where dragging occurred. The commutator is the end of the armature on which the brushes run. If that area is gouged or carbon covered the brushes can't make good electrical contact. The brushes may have been worn as well. Without pictures this about all I can suggest.

 

[Arkman]

Re: Trolling motor grind

wow...my eyes just melted reading that. i think thats a bad sign. I didnt understand hardly anything you said. I can try to take some photos this weekend and show you what it looks like.

After reading your post I found a diagram There doesn't appear to be anything fishy with the armature. No marks from junk in there or anything. The brushes look normal but I've only ever seen these so that might not say much (what do those do anyways?). Should the magnets spin with the armature. If I spin it by hand the magnets rotate. This seems odd to me, I would think they should be fixed in place. There are two long screws (#25 in the diagram) that hold the magnets from totally spinning around the inside of the case.

How would I clean the brushes? Or do I need to get new ones. Where would I find those? Could the brushes cause the motor to not work at a low speed? The speed setting is 1-10 and it would only work 4 and up.

Thanks for all your help! Don't give up on me, I'll figure it out eventually!

 

[Arkman]

Re: Trolling motor grind

It turns out that I had the brushing sitting on the shaft and not on the copper cylinder they were supposed to be on. Did that and now it works. Most of the grinding is gone as well. I would guess its from the broken magnet. I'll just have to keep an eye out for another one on craigslist to cannibalize to make a totally working motor. It works but you can hear the magnet moving when you first turn it on and when you turn it off.

Thanks for the help!
Josh

 

[Silvertip]

Re: Trolling motor grind

I can't believe this motor runs with the magnets free to rotate. Doesn't make sense. Are you sure you are looking at magnets.

 

[Arkman]

Re: Trolling motor grind

Yep they are definitely the magnets There are two screws that go in to hold the back on. I think the magnets get caught on those two screws so the cant rotate anymore. They can only rotate 1/2" before they stop on the screws.

I'm going to look for some new magnets but I need to get the bottom assembly I think. Any chance I could glue these back into place? I doubt it but thought it might be worth asking.

Any thoughts on why the motor doesn't work on settings 1-4?

Thanks again for all your help!

 

[Silvertip]

Re: Trolling motor grind

So what are the magnets fastened to that allows them to rotate. If each one was free, they would be stuck to each other. The way a motor works is the magnets are stationary and are fastened to the outside shell of the motor. The armature is the thing that spins. Current reaches the windings in the armature through the brushes that run on the commutator which is what you called the copper cylinder. Again, it is impossible to tell you why the motor only runs on position 1-4 since it shouldn't run at all with the magnets loose and rotating. The diagram you are looking at indicates item #11 is the "center section with magnets". It is stated that way because the magnets are not a field replaceable item. Only the assembly is available and that also indicates the magnets do not rotate freely. They simply must be stationary.

 

[Arkman]

Re: Trolling motor grind

Thanks for the reply. I know the magnets are supposed to be stationary. Thats why i'm so confused. I talked to a service center today and they said that part 11 is a housing that comes with the magnets. With that said, I can move the magnets in the housing. I'm not totally sure if they move with it all connected because I cant see them when its put together. I am 100% certain that they are the magnets. My theory is that when the motor turns on the magnets spin until they hit the two screws (part 25) which stop them from spinning. I dont know if that makes sense or not. I can take it apart again and take some photos of the armature in different positions and the magnets that will move, but since it is back together and working I'd rather not.

I hope you don't think I'm trying to be rude and say that you are wrong. Its quite the opposite. After reading about electric motors I started to understand how they work, thats why i was so confused. I can tell you with 100% certainty that the magnets will move, at least with the cover off. I can't see anything other then those two screws that would hold the motor in place.

Thanks for all your help!

 

[Silvertip]

Re: Trolling motor grind

For certain the magnets need to be cemented back onto the housing. If there are two of them, they need to be equally spaced from each other. This is probably what the grinding noise was from. As for speeds 1-4 all I can suggest is you fix the magnets and see if you get speeds 1-4 back. If not, the speed control in the head is probably toast.

 

[Arkman]

Re: Trolling motor grind

how should i fix them back in to place you think? What kind of adhesive?

Thanks again!

 

[Arkman]

Re: Trolling motor grind

Thanks for the info Silvertip. I got the magnets fastened back in the motor. I also cleaned up the insides carefully and now the grinding is gone (it was mostly gone before I glued them back down). And it also works on 2-10 now!

Thanks again for the help!