The extreme end of electrolysis

[Steadman Uhlich]

There is a good article on the subject of Galvanic Corrosion (and another photo of a outdrive corroded) with illustrations at:

Galvanic Corrosion - Seaworthy - BoatUS

[George DuBose]

When Skylark was renovated, we installed a Yandina galvanic isolator after the shorepower socket in the cockpit. She lost her ball zinc on the prop shaft near St. Pierre and I didn't have her hauled until I was in The Netherlands for two years.

No prop corrosion, no problems with marina wiring. No problems...

[Cheechako]

Yep, I've seen a new 1"+ shaft that looked like lace/spiderweb after 3 months in the wrong marina.
Of course if you've had powerboats with alum outdrives you understand how quick this can happen even without shore power sometimes. A very large zinc can disappear in 3 months summer use.

[mitiempo]

Originally Posted by a64pilot

But it has to be DC, right? Can't be AC?
So why do I hear all the horror stories about bad shorepower pedestals in Marina's etc.?
Is that a bunch of nonsense?
How can a neighbors boat be the problem, I've heard that for years, is it true?

On edit, if it can't be AC, then why do I have an isolation transformer isolating my boats ground on the AC side from shorepower?

I'm not doubting, but I am confused.

The problem in a marina if your boat doesn't have a galvanic isolator, or ideally a isolation transformer is the AC ground (green wire) connects you to everybody else's bad wiring scenario. It is DC, carried on the AC ground that is connected on most boats to the DC bus.