Tripping Breaker at Dock 84' Hunter 31

[31 Hunter]

Recently purchased a 84' HUnter. When I hook up the shore cord 30A (replaced) also replaced plugin to the boat, when I start drawing power it trips the ground fault 30A breaker at dock. The boat only has one main and two subs. One sub for outlets and one sub for hot water heater. I can turn the main on no problem. I can turn the the outlet on no problem until i plug in a fan or something and start drawing power and it will kick Shore breaker.
I have not found a GFI outlet in the boat. ( neighbors boat same make and year having same problem) Checked all connections on back of electrical panel.
When I try the hot water sub it kicks shore breaker.

For now I've been using a 30A to 15A running a extion cord into boat. I am running couple of fans and portable AC no problems.

Has anyone else ran into this problem? Any help will be greatly appreciated.

Thanks in advance,
The Black Crowe

 

[sail sfbay]

Ask the marina to check their shore power supply?

Might find these articles helpful:
How to deal with a boat that is trips the dock Ground Fault circuit breaker. - A discussion of the issues and possible solutions (pkys.com)
Shore Power Paradox Uncovered | Captain's Tips | Marinalife
Concerns About Your Dock Power Pedestals? We’re Here to Help (docksidepower.com)

 

[Mike Oldak]

time to share the cost of a marine electrian before something happens

 

[Ron20324]

In my marina we are required to use a shore power cord rated the same or more as the shore power breaker. We go around and unplug the offenders before a fire starts. THAT usually brngs the offenders into compliance.

 

[jssailem]

Hello “Black Crowe.”
Congrats to you on your boat and Welcome to the SBO Forum.

There is a possibility that it is yours or your neighbors boat. Not necessarily a GFCI plug on your boat but a error in the wiring of your boat. Possibly by a previous owner. Before the Marina’s started installing the new style pedestals this issue went along unnoticed.

The first article shared by @sail sfbay does a great job explaining the issue. Perhaps since this sounds like your first rodeo, you and the boat owner neighbor might go in together on the costs of an electrical survey by a marine electrician.