Originally Posted by LongJohn
I installed a new GFCI 110v outlet on the fly bridge. I pulled new 14/3 boat wire from the main AC distribution panel and terminated Hot to an unused breaker, and neutral and ground to the appropriate buses. Everything works fine except that a circuit tester shows "Open Ground". Investigation shows that every outlet on both 30A legs shows "Open Ground". Ground is good according to the tester at the dock power pedestal. Tester shows that the ground is good when the generator is running.
It's a 2005 Mainship 34T. It has isolation transformers but I don't understand them. Can some erudite person please help me understand, tell me where to look and what to fix?
If the grounds are showing open for all the original outlets, then the part about the new one is irrelevant. You need to find out why your boat's ground buss is not connected to the ground on the shore power at the dock. Obviously (to me), the first thing you should do is try a "known good" shorepower cord. Borrow one that works and try it.
Then trace the ground conductor through the boat from the inlet connection until you find a disconnected cable. If all else fails, call in a qualified marine electrician. You really want that ground for safety.