Fuses save trolling motors! Minn Kota Diagnosis and Fix by Amateur

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Frankenfish

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Hey everyone, I wanted to share my story and process so that it could serve as a cautionary tale and also share my fix with others who might have the same issue. I'm no trolling motor expert, but it felt pretty cool to fix the trolling motor myself. This is my first electric motor that I've taken apart.

I recently bought a 14ft Starcraft Sea Farer, 1978, that came with a 9.9 Johnson and a 2005 Minn Kota Endura 36lb. I've had a blast tearing out old wood, tinkering with the motor, and plugging holes. Even caught a few crappie in between all that.

On my first fishing trip - I got into some severe wind coupled with some motor trouble. I used my trolling motor to push myself away from shore to give myself time to get the outboard started. I quickly stowed the trolling motor and gunned it back to the boat ramp. When I got near the boat ramp, I realized I had left my trolling motor running. On top of that, my transducer that I hastily mounted to the trolling motor to get out and fish had wrapped it's cord around the prop and stopped it from turning. That meant the trolling motor had been seized in place, trying to run for the 7 minute ride back to shore. Of course, anyone who is stupid enough to wrap his transducer around the prop is also stupid enough to be running his trolling motor direct to battery. She's dead Jim.

After she cooled down a bit, I tried to run her. No good.
I hooked up the pins of my multimeter to the battery cables and turned the motor on - no continuity. It's important to note here that continuity is all I know how to use a multimeter for.
Thus began the disassembly.

I started at the top for continuity. Made sure the battery cables weren't shorting out. Eyeballed the rest of the cables at the top of the motor - everything looked good.

Took the lower portion apart, and kept testing for continuity. Tested the motor's rotor on all contacts for continuity because I was sure the heat had caused the wire coils to be damaged. Probably a nonsensical step because damage wouldn't affect continuity, right?

Next came the brushes. I was so thankful that only one brush popped out. Wouldn't want to lose the brush or spring. Wait a minute, why didn't that brush pop out? Aren't both brushes supposed to move.

Making a note of that, I continued to test continuity between this lower brush assembly and the wires that came down from the upper unit switch. Everything checked.

Next I removed the brush assembly and, sure enough, one of the brushes was retracted and melted into the housing. This wouldn't allow it to contact the motor. Sign of heat damage leading to loss of power to motor? I think we've found it! At first I tried to jimmy the brush loose, but it was in there good.
Luckily Minn Kota sells parts for 2005 motors. Boy was that a nice surprise. I ordered two new brushes, springs, and the plastic? housing part. Hopefully that replaces the extent of the damage.

Now the reassembly - here are some quick notes.
Do not email Minn Kota asking what the wax is in the nose of your trolling motor. They won't tell you any useful details. Guess it's secret squirrel juice.
With both brushes functioning, the rotor getting seated back between them was a huge challenge. I tried taping them back retracted, but that was a stupid idea and just ended with me and some tweezers trying to get all the tape pieces removed. What finally worked was the wife with two toothpicks holding the brushes retracted while I jimmied the rotor into place. Can't find a sentence much sexier than that.
Then from there, it was just getting the cables all fit back in to place. Minn Kota routes the cables in some creative ways. Take pictures on disassembly! Also I took note of anywhere the cables had rubbed and painted on some liquid electrical tape.

Hooked it back up, still without fuse now that I think of it (idiot), and she went to running! Going to get the fuse wired in to my boat and give extra attention to transducer cable management. Probably just mount it to the transom and save me worrying.

Hope you enjoyed the read and can learn from my trials. If you have any suggestions for folks on things I did wrong, please point them out!
 
Good warning. On small, simple jon boats I rig up, I like to use the Blue Seas circuit breakers you can manually trip. Since the boat typically just has navigation lights and a couple of other circuits at the most I run everything plus the trolling motor on a single battery. I use the circuit breaker like a battery switch with a single heavy gauge wire running from the battery positive to the breaker and then on the other breaker post I run wire to the battery as well as another wire to a switch panel of some sorts that can distribute power to everything else. Of course each of those circuits will need some sort of individual circuit protection as well. There are numerous ways this all can be done but I have found this works well for me.

BTW, these breakers can be attached to the 2" side of a 4x4x2" electrical junction box and then the box cover can be cut to hold 3 or more switches depending on size.

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Frankenfish said:
Do not email Minn Kota asking what the wax is in the nose of your trolling motor. They won't tell you any useful details. Guess it's secret squirrel juice.
My best guesstimate would be to fill the nose, as if otherwise empty condensation could form that could harm the internal electronics.
 
DaleH said:
Frankenfish said:
Do not email Minn Kota asking what the wax is in the nose of your trolling motor. They won't tell you any useful details. Guess it's secret squirrel juice.
My best guesstimate would be to fill the nose, as if otherwise empty condensation could form that could harm the internal electronics.

I emailed Minn Kota to make sure it was supposed to be there. I couldn't find any info about it online. Per their service department, "The wax that you see is protecting the speed coil that's built into that housing within that material. You can't see the coil, but it helps with different speed setting and to dissipate heat".

This could very well be the first document detailing Minn Kota's secret wax. Hope no black vans show up outside my house.
 

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