Minn Kota 3HP S/S trolling motor troubleshooting

[jeepwm69]

I have an older Minn Kota 3HP trolling motor that I bought in the late 80's. Hasn't been used a lot, and last week when I took it out for the first time this season, it didn't work. I tried turning it on and spinning the prop by hand, and got nothing but a whine.

I pulled the bottom end apart and discovered the magnets had become dislodged in the bottom, breaking one of them. After finding that parts for this motor are pretty much unobtainium, I expoxied the magnet back together and then expoxied the magnets back into the bottom case.

Now the motor still doesn't work. I ran a 12V jumper and ground to the red and black wires coming out of the board and going to the bottom end, and doing this the bottom does spin, so it would appear I have an issue in the top.

Is there anything in the top that can go bad on the component level, or does this pretty much spell bad board?

If the board is bad, replacements are not available. Has anyone tried using a simple speed controller like this one?

http://www.ebay.com/itm/1230V-30A-DC-Motor-Speed-Controller-/140357609233

Yes, I know the simple thing to do is to go buy a new trolling motor, but I like tinkering and fixing old things (much to the chagrin of the wife).

 

[gm280]

Is your trolling motor a single speed or five speed like so many were built then? If it is the five speed version, then the different speeds comes from the windings in the foot and not a circuit board in the head unit. When you went into the foot and found the magnets broken loose, did you look over both the brushes and armature to see in they were worn? Lots of times you can replace the bushes and turn the armature to level it out again and it will bring life back into the motor. If your problem is in the head unit, it most likely is a switch. So seeing how you like tinkering, take a look see and see what is the real problem. You never know, a few minor things and it could run for a few more years... JMHO!

 

[jeepwm69]

It is one of those "infinite speed" jobs. It has a smooth turning handle with no positions.

The windings and brushes look fine, and when I put power to the lower unit it spins fine, just at full speed.


There is a board that is covered with black rubber. There isn't much to look at to see what the problem is.

 

[jeepwm69]

Think I'm going to try this. http://www.ebay.com/itm/10-50V-60A-...os=unknow&ttype=price&talgo=origal&rmvSB=true

Looks like there are two red wires and two black wires going to the bottom unit. Would it be safe to assume that one set is for forward and the other for reverse?

 

[gm280]

Think I'm going to try this. http://www.ebay.com/itm/10-50V-60A-...os=unknow&ttype=price&talgo=origal&rmvSB=true

Looks like there are two red wires and two black wires going to the bottom unit. Would it be safe to assume that one set is for forward and the other for reverse?

Yes that is a simple PWM controller unit that will allow variable speed. They ganged up the power FETs to control that much current if you see the board. And if you are incline to replace your black covered unit, it would make yours run again. You sound a lot like me. I try to do things myself and I would actually build my own PWM unit as the replacement as well. If you go this way, let us know how it works out. I'd certainly like to know... :thumb:

 

[jeepwm69]

Will do. I asked the same question on another board and a poster suggested I wire in a diode to prevent "inductive spikes". Is this something you would agree with?

I'm not big on electronic stuff. I've wired around a lot on ATV's and Jeeps, but this is getting in a little over my head.

Still though, the motor runs with 12V applied to it, so I know it's simply a task of figuring out how to get that 12V to the motor and regulate the speed.

I was thinking of running a "Forward Off Reverse" switch, with one set of + and - wires going to forward and the other set going to reverse (again, based on the assumption that of the two + and two - wires going to the motor that one set is forward and the other is reverse). Does that sound right?

 

[gm280]

I don't think you need to install diodes and here's why. Being how the circuit on EBay is made specifically for large current motors, they already used the appropriate diode protection. So it would be redundant to install more.The MOSFETs are built with such protection now for that very reason. So my opinion is, you don't need them. If this was merely a non motor speed PWM controller then I would suggest them. But it states a DC motor controller and therefore was probably built with the latest designed power FETs with diode protection for the backflow EMF problems. That would be cheaper and a cleaner circuit board as well... JMHO.