how to test for Electrolysis with multimeter

[trav13]

Im getting some corrosion on my boat, and found a cut positive connector touching bare aluminum so hopefully the problem is taken care of. I used a multimeter after I fixed this connector just to check and see if there was anything else. I did this by touching the negative side to the aluminum trailer and the positive to the boat and Im getting -.26 volts. What does this mean and am I doing this right.

[welder]

If the boat is on the trailer and out of the water you should be reading 0 Volts .

If you get in the boat and put one lead of the Volt meter on the hull and one to the battery post you should read 0 volts.

Make sure your boat is NOT used for a ground for ANY electronics. Make sure there has been a 2 wire system for everything.

Let us know what ya get on the readings.

[ReelSong]

Silly question, but if it is an outboard, isnt the motor grounded to the hull just by being bolted to it and wouldnt you read 12 volts to the hull from positive post to hull anyhow? or is the motor ground isolated from hull somehow?

[welder]

Yes, your motor is bolted to the hull, and the motor itself is grounded to the alloy hull. BUT, we are not using the hull as our return lead (ground) to run the starter AND sitting on the trailer with the battery switch in the OFF position. The negative side of EVERYTHING should be isolated from the hull. This is why we run 2 wires to EVERY device in the boat and we do NOT run a ground wire from the NEGATIVE side of the battery to the hull.

And of course make sure your sacrificial anodes are in GOOD shape. If they are 50% in size or less, REPLACE them. They should also be kept CLEAN and in good CONTACT with the hull and/or your motor(s).

[ReelSong]

Got it, I understand the two wire process quite well, didnt realize you had the bat switch off and testing at that terminal. I thought you meant testing from positive post on battery to your hull with nothing on .

[Katoh]

Does this work on Diesel inboard as-well?

[welder]

Does this work on Diesel inboard as-well?

Yes it does , all boats.

[T-sole]

Sorry I'm a little slow. Which battery post, positive or negative?

[welder]

Try both posts just to see what you get . Just be sure your volt meter is set on DC.

[goatram]

I would think it would be to the negative terminal. The Positive will give a spark and a to your system.

Kmorin made a post about placing 1 Ground from the Battery to the Hull. All Components are run with two wires; one to the positive and the other to the Negative on a fuse block or to the battery

[goatram]

viewtopic.php?f=3&t=2262&p=18471&hilit=kmorin#p18471
For a good read on the Subject Matter from an expert

[welder]

I was hoping Kevin would some how get in on this.

Thanks John.

[Jonsboat]

Here is a good read if read in it's entirety

http://www.sailmail.com/grounds.htm

Here's another more to the original question

http://www.protroll.com/books/?id=5&p_id=4

[JETTYWOLF]

Here is a good read if read in it's entirety

http://www.sailmail.com/grounds.htm

Here's another more to the original question

http://www.protroll.com/books/?id=5&p_id=4

Your in Fresh water too, aren't ya.........damn yer boat must stay clean and slick as a whistle.

[Jonsboat]

Here is a good read if read in it's entirety

http://www.sailmail.com/grounds.htm

Here's another more to the original question

http://www.protroll.com/books/?id=5&p_id=4

Your in Fresh water too, aren't ya.........damn yer boat must stay clean and slick as a whistle.

Yes, mostly lake mi and superior, only salt I get is plastered on the front off the roads or what gets spilt eating, only clean it once a year and then not spit and shine.....although I have been considering it

Other then anode material is there a difference in protecting your boat from electrolysis in fresh vs salt?

[normster30]

I have a 2014 StarCraft alum boat with electrolysis damage. I'm getting 12 volts from pos. post to hull with voltmeter. It is somewhere in factory wiring. I'm dealing with the factory to fix under warranty. Just wondering if anyone else has had this problem.

[MacCTD]

I believe it is impossible to isolate the hull as the outboard is grounded and and attached to the hull, my Pacific is the same way. Just make sure you have the correct anodes installed on the engine and hull.

[MacGyver]

Not only is it not possible but ABYC recommend having a cable the size of the negative terminal battery cable going from the negative bus to the hull. This cable is needed to help protect the hull from corrosion.