GFI problem pluging in shorecord

[crosswind]

Greetings everyone!!
I have recently sold my 1979 58' Hatteras YachtFish to some really nice people. During the survey, the surveyor plugged in a 30 milliamp GFI box to test hooking up to shore power with a GFI pedestal, as a lot of pedestals are now GFI. (My dock does not have a GFI pedestal).
And of course, it tested that it would not be able to plug into GFI!
We immediately hired an electrician who found some bad breakers that have been replaced. He also found that the galvanic isolator needed replaced, which we did as well. Ugh! We still can not plug into a GFI pedestal. Have been looking for a grounded neutral, but have not found one yet.
Let me back up... You can turn off every breaker in the breaker box, including the mains, and the problem is still there. However, turning off the breaker in the switching box (to the left of the lower helm) makes the problem go away. We switched the shore cord 220V 50AMP to the port side and the problem was still there.
I have read some posts of a boost transformer, and wonder if it could be malfunctioning.???
I don't even know if the boat has one, but according to owners club, anything after 1978 does.
Please! Any suggestions would be appreciated, as the poor people who bought the boat need to take it home.
The electrician says that the green (ground) wire going to the pedestal shows .5 amp.
Thanks!!

[Pascal]

I would start by physically disconnecting major appliances like oven, washing machine, stove etc. as many household appliances bond the ground and neutral inside. Turning off the breaker doesn’t help diagnose because it only turns off the hot, not the neutral.

[oscarvan]

May have to do some hard wired items too. Water heater, stove, old battery chargers.

[crosswind]

thanks for the info but I did forget to mention the breakers in this boat are two pole breakers breaking the hot and the neutral when switched off

[SKYCHENEY]

We were at a marina that just had a new "marina guard" electrical system install. It had about 250 slips mostly seasonal and many of the boat owners were not happy that they had a problem. Some ended up hiring electricians, some figured out what was wrong on their own and others just installed isolation transformers.

My first thought would be to turn off all breakers if they break the neutral like you say and then turn on one at a time to see when the problem shows up. At least you could narrow it down to certain circuit.

[ocean spirit]

Just had the same issue on my 71 model 53. When stove/washer breaker was turned on the docks panel would show a 340 mil amp spike. Dis connected washer and panel showed within limits. Then reconnected washer leaving stove disconnect and again we stayed within limits. Just order another 220 breaker from Sams so they can have there own circuits. One other item the current 220 breaker is powered directly from selector switch. Good luck

[steve c]

I had the same problem last spring when my marina installed new wiring and pedestals when they
replaced the fixed docks with floaters. My boat had the ac neutral grounded to the dc panel in the engine room.
This solved the initial problem. At the time I was using a y cord o supply 50 amp 240. The y cord continued to
trip the breaker and I was informed that smart y cords would not work with the new system. Also, the electric
stove would present a problem because it was 4 wire. I don't use the stove so that was not a problem and the
marina installed a 50 amp service to solve the y cord problem. Many older boats were wired with the ac neutral sharing
the dc ground.

[oscarvan]

Is there a way I can check my boat before I get to a marina with new setup?

[Boatsb]

Is there a way I can check my boat before I get to a marina with new setup?

If the boat has a functional gfci or ELCI it may be sensitive to the one on the dock. There is only one needed and having one on the dock can be problematic.

[oscarvan]

If the boat has a functional gfci or ELCI it may be sensitive to the one on the dock. There is only one needed and having one on the dock can be problematic.

No my boat is pretty original, and as we established without transformers. So I want to determine if I have ANY voltage loss to ground on the boat BEFORE I end up in a marina that won't let me connect to their newfangled shore power.