Driving me nuts

[gleninaz]

I have an '04 Champ 203. We put new batteries in a couple of months ago and a new Ultrex. All worked great for a few trips then the motor would barely turn the prop. I tested all 3 batteries and they have 12.6 volts each. I tested the TM plug and it had only 12 volts. This morning I tested between battery 1 and battery 3 at the TM posts and got only 25.6 volts. Next test it was 12.6 volts? I have an old push button 40 amp breaker and will install a new MK 60 amp tomorrow but am thinking maybe one of the 6 guage jumper wires is bad. Anyway I am hoping it is the old breaker.

[CatFan]

If you had a bad jumper wire, you wouldn't measure any voltage at the plug. If you have multiple jumper wires, I assume you have a 36V motor?

Odds are if you measure both 25 and 12V at the plug you have a 3 or 4 wire system to the front and were on a different pin with at least one meter lead for each measurement. That also would mean you might have two breakers.

[Jonestrollingmotor]

As mentioned above, do you have a 4 prong plug, and if so, how many wires are going from the batteries up to the trolling motor. Like Catfan said above, I'm guessing you have 4 wires, 2 coming off one battery and 2 coming off a pair with a jumper in the middle. When you say "TM" post, I'm assuming you're talking about the battery post themselves. If so and you have the setup mentioned above, you shouldn't read any voltage unless the trolling motor is plugged in. The setup will help us diagnose.
John

[gleninaz]

I have a 3 prong TM plug. I tested at the battery posts for the + and - that go to the trolling motor. It is a 36 volt motor with 3 batteries in series. It all worked then the trolling motor just went to a very low level and not even enough to use the powered foot pedal. I removed the plug at the front and touched the two wires and only got 12 volts so something is messed up from the batteries to the front.

[wmitch2]

Remove the plug in and take a pic of the front and back with the wires attached and post it here. It's hard to diagnose without seeing exactly what you have.

[CatFan]

I have a 3 prong TM plug. I tested at the battery posts for the + and - that go to the trolling motor. It is a 36 volt motor with 3 batteries in series. It all worked then the trolling motor just went to a very low level and not even enough to use the powered foot pedal. I removed the plug at the front and touched the two wires and only got 12 volts so something is messed up from the batteries to the front.

What you are suggesting isn't really possible. If you have 36V across the string of batteries, you have 36V at the front unless the wires to the front are on the wrong posts.

Nothing could happen to the wires along the run to change the 36V to anything different except 0V. A bad breaker, bad wires, bad plug etc. can't do that.

For 36V with jumpers at the battery, you only need two wires to the front. The one on battery 1 negative and the one on battery 3 positive. Disconnect any other wire going to the front and measure your voltage at the plug again. Be sure you have a breaker in the positive lead from battery 3.

If you have 3 wires to the front, it's very possible to measure 24V between two wires and 12V between two wires. For example, wire A to wire B could be 12V, wire B to wire C could be 24V, but then A to C should be 36V.

[Jonestrollingmotor]

From the first post " I tested all 3 batteries and they have 12.6 volts each. I tested the TM plug and it had only 12 volts. This morning I tested between battery 1 and battery 3 at the TM posts and got only 25.6 volts." To get this reading, one of the batteries would have to be completely discharged and would explain the slow down of the trolling motor. When you "load" the system it can be enough to drop the voltage if a battery is bad.
Pay particular attention to the polarity on the voltmeter. It is possible you have two batteries with 12.6 and one with "-12.6" (battery charged up with reverse current) in which case it would/should read between 12 and 13V when testing in a series string. (12.6+12.6-12.6).
John

[gleninaz]

I have a load tester and will try that tomorrow. May be a bad battery.

[Jonestrollingmotor]

Make sure you check the polarity of the batteries as I mentioned before you try load testing.

[CatFan]

I have a load tester and will try that tomorrow. May be a bad battery.

just measure with a meter from bat 1 neg to bat 3 positive. No load test needed.

[gleninaz]

That is what I did this morning. Meter read 25.5 volts then it would read 12.6 volts.

[CatFan]

That is what I did this morning. Meter read 25.5 volts then it would read 12.6 volts.

On the battery terminals? Not physically possible.

[86 inches]

Did you get it figured out, Glen?

[Jonestrollingmotor]

That is what I did this morning. Meter read 25.5 volts then it would read 12.6 volts.

If this is a reading off the same two battery terminals at different times, and you didn't change anything with the wiring ie: plug the trolling motor in or connect some other "load", it isn't physically possible as Catfan said. If it did truly happen, I would verify the meter is good and on the right settings.
John

[gleninaz]

I am going to fry a turkey then Friday will install the new breaker and test everything with another meter. I know there was a day that water got in the plug to the charger and blew a circuit breaker so maybe a jumper wire got burned. If I can't figure it out I will take the boat to my Minnkota repair place and let them figure it out. Thanks for the help.

[billnorman1]

If he has a 3 wire system, and two of the batteries run 12 volts in series giving him 24 volts with a 0 volt reference, and another 12 volt battery providing 12 volts couldn't he have a jumper inside the male trolling motor plug making it into 36 volts?
If there is a jumper between the + side of the 24 volt pair in the back, and the other 12 volt minus, and a wire (the third wire) has that 12 volt + on it could this be the factory configuration to give hin 24/36 volt options? Anyhow, with a 24 volt 4 wire system I've had this internal jumper get loose and cause total 24 volt failure. It wouldn't hurt to take the back off the male T/M plug and check all the screws inside.

[CatFan]

If he has a 3 wire system, and two of the batteries run 12 volts in series giving him 24 volts with a 0 volt reference, and another 12 volt battery providing 12 volts couldn't he have a jumper inside the male trolling motor plug making it into 36 volts?
If there is a jumper between the + side of the 24 volt pair in the back, and the other 12 volt minus, and a wire (the third wire) has that 12 volt + on it could this be the factory configuration to give hin 24/36 volt options? Anyhow, with a 24 volt 4 wire system I've had this internal jumper get loose and cause total 24 volt failure. It wouldn't hurt to take the back off the male T/M plug and check all the screws inside.

He mentions he has 6 gauge jumper wires which indicates it’s jumped at the battery, and any jumper wire failure would result in no voltage at the TM.

[billnorman1]

He mentions he has 6 gauge jumper wires which indicates it’s jumped at the battery, and any jumper wire failure would result in no voltage at the TM.

Not really.

[CatFan]

Not really.

Yes, certainly. A failed jumper in any series circuit will result in a non-working TM.

[billnorman1]

Yes, certainly. A failed jumper in any series circuit will result in a non-working TM.

I'm aware of the necessity of a complete current path in a series circuit, my electrical experience, although 55+ years old still recognizes that. Since he has three wires to the front I don't see why he shouldn't check the screws in the male plug, this is a common source of failure in an older system.
The boat maker may have wired the boat with 0 volts, 24 volts and 12 volts at the female plug and jumpered the last 12 volt battery inside the male plug to make 36 volts. This would give him the option of using a 24 volt motor if he so desired and not use three batteries.