Electrolysis - TM corrosion?

[mattfish11]

What causes electrolysis appearing on the trolling motor? Relatively new to me boat - just installed an Ultrex and noticed I'm getting some white powder on my prop nut (eliminator prop nut).... Also 2 or 3 tiny spots of white on the trolling motor nose cone.

What do I look for first as far as causes?!?

[mattfish11]

FYI - I'm running 24v trolling motor directly to 2 optima batteries. Only other thing these batteries are hooked up to is the on board battery charger.

[CatFan]

Miswired batteries, particularly noise reducing grounds and jump start systems, or storing the boat in the water at a marina are first choices.

[mattfish11]

Miswired batteries, particularly noise reducing grounds and jump start systems, or storing the boat in the water at a marina are first choices.

Thanks or the response CatFan. It's weird because I don't have any noise reducing grounds - or jump start systems... And I don't store the boat in the water ever.

Is there anything in the trolling motor I could check? What would I be looking for?

[CatFan]

The underlying issue is that your TM case is at a different voltage than something else in the water nearby. Likely the hull or outboard lower unit, though those should be at the same voltage. Normally what happens is that there is a connection between one of the middle wires on the TM system to outboard ground which gives you 12 or 24V difference between the TM housing and outboard LU and current flows through the water.

First thing would be to verify that your TM is actually seeing 24V at the front of the boat. Measure at the TM wires themselves.

You can try measuring between the prop nut and outboard battery negative with a voltmeter. Turn on master power and your TM breaker. Try combinations of equipment like electronics on and off.

What is connected to your cranking battery? Second battery for electronics? Outboard powered charger?

What things like transducers, hydrowave etc. are in the water while you are fishing?

Anything non-standard on your boat?

[mattfish11]

The underlying issue is that your TM case is at a different voltage than something else in the water nearby. Likely the hull or outboard lower unit, though those should be at the same voltage. Normally what happens is that there is a connection between one of the middle wires on the TM system to outboard ground which gives you 12 or 24V difference between the TM housing and outboard LU and current flows through the water.

First thing would be to verify that your TM is actually seeing 24V at the front of the boat. Measure at the TM wires themselves.

You can try measuring between the prop nut and outboard battery negative with a voltmeter. Turn on master power and your TM breaker. Try combinations of equipment like electronics on and off.

What is connected to your cranking battery? Second battery for electronics? Outboard powered charger?

What things like transducers, hydrowave etc. are in the water while you are fishing?

Anything non-standard on your boat?

Again - appreciate the info.... I have my work cut out for me. I'll get you some answers after a little digging.

Here are some I can tell you now:
What is connected to my cranking battery - Everything but the trolling motor. I have 2 HDS 7 and an HDS 8, compartment lights, onboard charger, bilge/aerator pumps, Rigid trolling motor light. Come to think of it - could the issue have something to do with a 12v trolling motor light connected to a 24v trolling motor? I know others have done it without issue but....
Don't have a second battery for electronics, nor do I have an outboard powered charger (although it has an alternator built in)

What things are in the water while fishing? - Transducers(tm ducer, transom 2D and transom LSS) and the trolling motor.

[Lowerider58]

I'd be very suspicious of the trolling motor light. Do the voltage check between the TM prop nut and the starter battery negative with the light connected and disconnected. How exactly is it wired?

[Rip Bass]

Make sure when you grounded the TM light that you did not use a ground from the cranking battery. If you are getting power from the TM batteries,it needs to be grounded to the TM batteries too.

[CatFan]

I'd be very suspicious of the trolling motor light. Do the voltage check between the TM prop nut and the starter battery negative with the light connected and disconnected. How exactly is it wired?

Me too. If the light it getting its power from the cranking battery, it could get weird.

[mattfish11]

Make sure when you grounded the TM light that you did not use a ground from the cranking battery. If you are getting power from the TM batteries,it needs to be grounded to the TM batteries too.

TM light is supplied AND grounded to the cranking battery

[Texas Larry]

It looks kinda like a metal boat, is that correct? If so, you may have a ground loop going on, two different grounds- causing a differential in potential resulting in current flow between two grounds. That would be caused by something being grounded to the hull instead of a ground wire directly to the battery. Could also be caused by a bad ground wire that is allowing the TM to be grounded through the hull instead of a ground wire. Does the light have a ground wire all the way to the battery - That's where I would start? If you just installed the Ultrex, you definitely have a problem - that's a lot of corrosion.

[mattfish11]

OK guys... Was going through the battery compartment and noticed a black n red set of wires were connected to the 1 tm battery. Have no clue what it is for - and couldn't get it figured out. There was an inline fuse on the one wire - I took a look and it's corroded bad. I'm assuming this is where the problem is. I taped up those wires and tucked them out of the way. Hopefully this was my issue.

Thanks again CatFan and everybody else for your insights!

[ThaiStick]

OK guys... Was going through the battery compartment and noticed a black n red set of wires were connected to the 1 tm battery. Have no clue what it is for - and couldn't get it figured out. There was an inline fuse on the one wire - I took a look and it's corroded bad. I'm assuming this is where the problem is. I taped up those wires and tucked them out of the way. Hopefully this was my issue.

Thanks again CatFan and everybody else for your insights!

Hi there I know this thread is old. Just want to see if the corrosion went away after you tucked away those wires.
Thank you.