Minn Kota Prop Stop & Power Loss

Hi All!
I have two MKs on a pontoon and recently noticed a loss of power. Thought it was the trickle charger, (2 banks going to four 12v batts), but it’s working. The batteries are getting a full charge. When I start from the dock the boat moves out as usual then there is a distinct drop in power/speed. On my last test run the starboard motor made a humming sound, stopped, spun, stopped again, then I cut power. I eased the power back up and both props spun, but again at low power. I don’t think MKs can have a spun prop with the pin in the shaft, but pulled the prop, the pin was intact. The shaft spins freely by hand. I opened the motor and all looks good. No rust, no water.

Anybody see this before? I can’t figure out what’s wrong. I’m thinking it may be the motors, but the one I opened “looks” good.

Any input would be appreciated!

gt

How old are your batts? Since both motors are having the same problem the batts are probably to blame. Just because they are “fully” charged doesn’t mean they will support the load. Continual run time on weak batteries is very hard on motor brushes and armatures. When voltage drops amps increase and cause damage. Have the batts and or the power cables checked out.

X2 with slowpoke. I would start by checking the batteries. Most auto parts stores have a tester that can put a load on them to see if there are good. It only takes one battery to be bad to cause problems with the other when they are connected together. Now this doesn’t explain a loss of speed in both trolling motors. Unless the lost of thrust in one motor is making that kind of difference and the other one is going as best as it can. Is it just one motor not working and the other is fine?

Have your batteries load tested.Sounds like voltage drop under load.I have had batteries accept a charge,and show 12.6v on a meter.But put a trolling motor load on it and voltage dropped down to 10.8v.

Someone correct me if I am wrong, but I don’t think load testing a deep cycle battery tells you much of anything. Load testing should be used for cranking/starting batteries.

I think you can load test deep cycles….o”Reilly’s did it for me.

This sounds like bad batteries to me as well. They show full but under load immediately lose power. Have you checked the water? Have a bad cell in them?

I’d also check that charger. Most will throw error codes of the batteries are bad. If it’s an inexpensive charger and doesn’t throw a code it might be faulty.

Matt Moen wrote:

I think you can load test deep cycles….o”Reilly’s did it for me.

Sure, you can, but I don’t really think it’s giving you a meaningful result.

Ralph Wiggum wrote:

Someone correct me if I am wrong, but I don’t think load testing a deep cycle battery tells you much of anything. Load testing should be used for cranking/starting batteries.

You are correct Ralph! Automotive load testers are not meant for Deep Cycle batts… regardless of what parts stores tell you.

Two of the batts are a year old and two are new. I’ve checked the brushes on both motors and they look good.

They both work, then they both work slow together. Could one losing power drain and equalize the other?
On my last run the one motor stopped spinning for a moment, then I cut power and brought it back and it them spun. that’s one one I recently opened and it all looks good. It IS however a 20 year-old motor.

Two are new and two are a year old, but will check water in all to be sure. Thanks!

The hand controller passes through two electronics modules. Could those have an effect on power to the motors? Everything is interconnected.

I’m going to pursue a deep test on the batts, (there’re just four of them and a pain to remove), but that seems a likely first stop.

Anyone know if those modules could be an issue? (I also sanded all the connections to shiny bright, just in case that was it. It had no effect.)

And thank you all for your wisdom!

Check the crimp on the power cables with a ohm meter from end to end disconnected. It should be very low. If it isn’t they are junk and you need to cut the cable back to clean copper before putting new ends on. Check this FIRST before removing the batts. What voltage are these motors? How do you have them connected? Do a voltage drop test across the batts while running one motor. If the voltage goes below 12v the batt is either not fully charged or its junk. You should be able to isolate one motor at a time to pinpoint if there is in fact a bad one. If its not the cables I’m still leaning towards the batts. Like Matt asked have you checked the water in each cell?

Thanks slowpoke. I think you summarized the last step. Water is good in the batts, so I think what I’m left with is doing a load test and following your advice on the cables.

Like the others have said, it sure sounds like a battery/power issue and not the motor issue.
You said you have two Minnkotas, are these 12v, 24v, or 36v?
You mentioned 4 batteries, but just a 2 bank charger. How does this work? How are you batteries wired?
This whole system seems a bit complex, which is another reason why battery/power issue is the culprit.

The way I am guessing he has it wired is two batteries to one trolling motor and each bank of the charger is 24 volts. Please let us know Mr. King if you have it another way. Pictures also help.

Ralph Wiggum wrote:

<div class=”d4p-bbt-quote-title”>Matt Moen wrote:</div>
I think you can load test deep cycles….o”Reilly’s did it for me.

Sure, you can, but I don’t really think it’s giving you a meaningful result.

The digital testers at most auto parts stores have a setting for testing deep cycle batteries. Make sure they know you want it tested on the marine/rv setting. They don’t test many marine/rv batteries and the auto battery setting is the default setting on the tester.

Charge your batteries check voltage unhook everything let the batteries sit for a day or two if voltage drops you know the batteries are weak. This is one of the surest ways to check a battery, I have had new batteries that went bad after only 3 months.