Weird electrical Issues with my Tin Boat

[Hooked on Legend]

I have a 17' Express with 36 Ultrex and a new 75 merc 4 stroke. Checking things out with a volt meter I found that my boat was a ground. I unhooked all 4 neg. leads one at a time to find a bare wire or something. Still could not Isolate the source of the ground. Touch the volt meter lead to my battery post and the other to the boat and it would read 12.68 volts. After many hours and frustration I unhooked every + and - lead to all 4 batteries. To my surprise I still metered voltage. Like 4.6 volts on the neg post to boat and 6 volts from the positive post to the boat. Called a buddy, he went out and check his tin boat and also read 12 volts from positive post and negative lead to the boat. 12 Volts.... After that it was BEER Thirty!!!!!!! Has anybody else been thru this???

[Mechanic Bob]

Your motor is grounded to the boat. Yes, if you test the positive on the battery to the boat, you will read battery voltage.
So any ground wire, can and will ground through the boat and motor. Mind you there is a relative high resistance, but there is continuity.
Stray voltage could be coming from different sources or a Faulty meter. Also, is your boat on the trailer and the trailer connected to a tow vehicle?

[King_Fish]

I have a 17' Express with 36 Ultrex and a new 75 merc 4 stroke. Checking things out with a volt meter I found that my boat was a ground. I unhooked all 4 neg. leads one at a time to find a bare wire or something. Still could not Isolate the source of the ground. Touch the volt meter lead to my battery post and the other to the boat and it would read 12.68 volts. After many hours and frustration I unhooked every + and - lead to all 4 batteries. To my surprise I still metered voltage. Like 4.6 volts on the neg post to boat and 6 volts from the positive post to the boat. Called a buddy, he went out and check his tin boat and also read 12 volts from positive post and negative lead to the boat. 12 Volts.... After that it was BEER Thirty!!!!!!! Has anybody else been thru this???

So is there actually an issue / problem you are experiencing? Or just an observation?

[GeauxTide]

I'd look at the wire. Many 17s come with a 12v system, so the wire will be much smaller. I'd use 6 guage on a 36v system.

[Hooked on Legend]

The trailer is Not hooked up to the truck. The safety chain is not touching the ground. 2 tires and and hard plastic wheel on the Jack.

[Hooked on Legend]

I'd look at the wire. Many 17s come with a 12v system, so the wire will be much smaller. I'd use 6 guage on a 36v system.

I ran my own wire for the 36. 8 gage

[Hooked on Legend]

So is there actually an issue / problem you are experiencing? Or just an observation?

Just an observation. But with my new Merc I do not want any problems.

[blkfalc4]

It should be 'grounded' (motor mounts) to the common. You'd have electrolysis problems otherwise.

[Crappie Bob]

I ran into that with my Tacker 185 XT. Unhooked. moved, cleaned, same thing and never changed. That was 2 years ago and no issues to date.

[Hooked on Legend]

It should be 'grounded' (motor mounts) to the common. You'd have electrolysis problems otherwise.

The reason I checked the boat for being a ground is back in December when I was walleye fish I noticed electrolysis on my Ultrex motor. Come to find out the motor had water in it and I thought that was the cause of the electrolysis. Which I'm sure it was. No more electrolysis after getting the troller fixed.

[King_Fish]

The reason I checked the boat for being a ground is back in December when I was walleye fish I noticed electrolysis on my Ultrex motor. Come to find out the motor had water in it and I thought that was the cause of the electrolysis. Which I'm sure it was. No more electrolysis after getting the troller fixed.

Had water issue with my MK Fortrex as well, the O-ring on front end of power head was kinked and the bolts were loose. I rebuilt it and it's now fine. I'm planning to measure my battery to hull this evening

[King_Fish]

FWIW at this point, I checked my electrical system isolation from hull last night.

- My TM battery system (24V) is completely isolated from hull.
- My Main (12V) battery distribution (-) is tied to hull i.e. returned through the OB motor connection, as a wise man stated above...