I have the same problem too, I found if you shut off the breaker in the boat prior to shore power being plugged in it will power up with out tripping the breaker.

Have you taken a volt meter to the boats end of the shore cord (plugged into the dock, but not the boat)?

Start at the dock recepticle and work your way forward 1 step at a time.

If it's tripin, I would look for a short more so than an open.

Did your dock ever work correctly? If you would like you can PM me with your phone number, I will walk you thru the trouble shooting steps. You should have 1 hot, 1 neutral, & 1 ground.

I never had a boat before that had shore power, so I don't know if it ever worked. I've checked the wiring connection and it looks correct....

I hope this gives you some reference, after reading your posts I would guess that you have a hot ground or partial leak to ground from the dock hook-up. If you are at a Marina I would just have their electrician deal with it and save yourself the hassle and responsibility.

If it's tripping the breaker in the cabin with everything else off, I would have to think that the breaker is a GFI breaker (Like Turbojack said). An open neutral would cause an immediate trip of a GFI breaker, as well as a ground fault. The first thing I would do is determine if it is a GFI breaker (GFCI), because if it is, It's alerting you to a potentially unsafe condition.
Then I would get the dock line checked by a professional. I worked for Leviton Mfg in their R&D/ UL certification lab for over 10 years, and I've seen a lot of flakey GFI problems, as well as a lot of dead people because of them. Be careful.

Something is wired wrong on the dock or boat. Reversed polarity and a grounded neutral in the boats wiring is my guess. Many "home" electricians will ground the neutral in the box when wiring. This doesn't matter in homes. But in a boat, if you get the polarity reversed in the box or cord, it will ground the hot wire. If it's not reversed, it will work fine.
Gary

You can not use a ground fault breaker at the house power panel or on the receptical that the power cord plugs to the dock. That will trip the breaker, much like a rv. I'm betting you a ground ground somewhere in the existing line.

That's the problem, then. I have a GFI breaker on the dock that everything is fed from. Did it for safety reasons. Why does that cause the breaker in the boat to trip?

I'll call Formula support and ask them as well...

The breaker on the dock is not tripping corrrect? Dock breaker being GFIed or not is not going to cause you main breaker to trip on your boat. If the dock breaker is not tripping when the breaker on the boat is tripping you may have a miss wired plug on the dock.