Have a 2002 formula 353 with onboard charger and refrigerator. I have the shore power connected to maintain my batteries but every time i flip the bat charger breaker it trips the main breaker. I tried the refrigerator breaker and it trips the main also (refrigerator works fine on 12v breaker). The only breaker that wont trip the main is the outlet breaker but it does dim the green shore power light with nothing even plugged into it. I'm thinking the shore power is not supplying enough power but it's the same outlet that worked all last year nothing has changed. Looking for ideas here.

If the main is tripping, you either have a bad main or a dead short somewhere. Unplug the boat and put a meter on the hot leg and check resistance to ground with devices unplugged and breakers on. You should be able to find out if you have a short that way.

When did this start and how long have you had the boat?

I dealt with this a few years back on a Formula of similar vintage. I was stumped and contacted the Formula dealer. They looked at the boat and were likewise stumped. The dealer contacted the factory and the factory provided the fix. I would contact the factory.

Most likely have a loose neutral contact to the shore power cord. May be in the cord, could be in the socket in the boat where the cord plugs in

Are u tripping the gfi? whole nuther issue.....

If you are not familiar with boat shore power option, take it to a mechanic who knows what they are doing. Friend bought a used Formula couple years ago had very similar issue, we opened it up and there was some burned wiring in the A/C side of the wiring due to corrosion. I was going to fix it, but he wanted a local marina to do the work. They diagnosed the issue and had it repaired in an hour. No more issues and working perfect.

So i put a volt meter on the garage outlet, extension cord and the "pigtail" that plugs into the boat all checked out. Hooked it all back up checked voltage at the main breaker and seeing full 120v. Put everything together now its working only thing i can think is maybe it had some moisture or i didnt have the pigtail fully seated. Just going to keep an eye on it for now