Forbidden - Using an Alloy Boat as an electrical ground - Causes Corrosion

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PappaPepper
Donator '20
Posts: 12
Joined: Mon Aug 24, 2020 5:23 pm
Location: Kitsap

Forbidden - Using an Alloy Boat as an electrical ground - Causes Corrosion

#1

Post by PappaPepper »

I've attached a few photos of corrosion that is occurring all over my boat. In talking with pacific I can't tell if its from poor electrical connections or just general neglect.

In doing a little electrical checking I found that there are three wires coming off the negative terminal of the battery. One to the Main Motor, One to the Kicker, and one to the negative bus. When I lift all three leads and measure from each to ground I find Hull to Main Motor Negative Wire ~5 ohms, Hull to Kicker negative wire ~5 ohms, Hull to negative bus ~3MegaOhms.

When I lift the negative leads at the Main Motor and the Kicker then measure from the motor to ground near the motor its about 1 ohm for each. And the negative wires now both disconnected from the battery and motors are near infinite resistance.

In short my main motor and kicker are grounded to the hull. Makes some sense as they are bolted to the hull. But they also have a direct electrical line running from the battery terminal to the engine so I'm not sure if this is a violation of the rule to never use the hull as a ground. I believe all the other connections are good, or at least not grounded because they show near infinite resistance at the negative bus going to the neg bus terminal.

Could these motors being connected to the hull be causing the general area corrosion? Is this normal that the is no resistance from the hull to the motors?

In one of the photos you see the boat logo. Around that logo in a large square pattern I rubbed some Corrosion Block on the surface to see how effective it might be.To me it seems like it improved a bit - but maybe olive oil would have done the same. In another thread I had mentioned refinishing the hull, but realize that might just be another nightmare going into the Fall. Are there any recommendations on how to clean up this corrosion? Maybe where the corrosion is coming from? Its been on the hard for 18 months now so I imagine it can't be from salt water unless it was never washed after its last use (i could imagine that being the case).

Again, thank you all in advance for the
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kmorin
Donator 08, 09, 10, 11, 12, 13, 14 15, 16 17, 18, 19, 20
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Re: Forbidden - Using an Alloy Boat as an electrical ground - Causes Corrosion

#2

Post by kmorin »

P'Pepper,
give the archives a shot? We've been over this quite a bit.

NO your engines bonding to hull can't cause open air 'flowers' only a film that holds water vapor can do this. So if you have Nyalac (sp?) it has got to come off and be re-applied or, if the mill scale wasn't removed (via acid washing) then that has to come off.

Only place your engine's potential stray current corrosion would show up is below the waterline. This is crevice corrosion caused by failed film on sheet/plate.

Think Zep-A-Lume!

Cheers,
Kevin Morin
the AAB.com Forum millscale 'gnat-zee'
kmorin

PappaPepper
Donator '20
Posts: 12
Joined: Mon Aug 24, 2020 5:23 pm
Location: Kitsap

Re: Forbidden - Using an Alloy Boat as an electrical ground - Causes Corrosion

#3

Post by PappaPepper »

Right on! I'll get back into the archives. Once I find a good thread I'll link it in this post too. Thank you!!

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