Originally Posted by MarkSF
Do you have a galvanic isolator? If not, you probably should.
Your problem is most likely the opposite of a bad ground on your boat. Yours is too good. A galvanic isolator pretty much deliberately disconnects your ground from the marina's, until you put serious current into it. Maybe a bad one on someone else's boat?
The galvanic isolator is a capacitive coupling designed to allow AC currents of about 60Hz to pass while blocking DC currents. The reason for this is that the water
is still your ground for fault currents.
120V AC can kill you and that's why there's a third wire. The third wire is supposed to carry any current that might kill you down the wire to ground. Presumably the ground path through this wire is going have a lower impedance than you and most of the current will flow that way.
But remember this is AC current not DC current. It's an error to refer to 'serious current'. AC current of any magnitude should flow through the isolator but it's not supposed to be doing that. If it is there's a fault in your AC equipment
is a DC phenomena and that's why there's an isolator. You are trying to break any DC link between the AC system ground and the water/boat ground. It's possible that for various reasons there could be a potential difference between your AC ground and the water/boat. Even a small difference will result in current flowing which will plate or deplete below the water
line metals depending on which way the current is flowing.
This isn't my area of expertise but I have put some thought and reading into it and it's my opinion that it's not a simple phenomena and that what most people have to say about the subject is anecdotal. If I had to guess I would guess that less actual science has been done on this subject than people would expect.
Presumably if you have the isolator you should be Ok to remain plugged into shore power
. It should be difficult to mess up your wiring
. You would have to have below the waterline metal at some potential other than that of the surround water.
In the case I experienced last year I believe my issue was caused by a nearby boat who had some 'professional' wire up their bowthruster backwards (couldn't possibly do that on a metal boat!). I believe that it was proximity through the water that ruined my propeller
last year not anything to do with the shore power
. But I still wonder and it's all too complicated to be able to go to that guy and force him to cover my propeller even though I never had an electrolysis
problem before. How do you prove it? Hire another 'professional'?