Inverter not charging batteries

[wesca]

I'm helping a friend who has 80's vintage 26' Sea Ray. It has a Hart Interface 2500 on board. Recently he ran the system to full discharge by running a small space heater(110vac) and some ac lights without the shore power on. After replacing the starting battery, he ran the engine to charge the house bank. At this point with shore power from the dock on, when he closes the main ac breaker on his panel it stays on for about 5-10 seconds, then trips. At the same time I hear a click in the inverter. None of the exterior resets pop out on the inverter. There are no ac loads connected, all ac breakers are off. The inverter works to supply 110 ac off the house bank, but during the short time the main breaker stays on I don't see any voltage rise on the inverter panel, nor measure any rise at the batteries. Batteries are at 11.88 vdc, also reflected on the hart panel. The two 6 vdc batteries have plenty of water, look to be fairly new, good connections, etc. The charging circuit/transformer/rectifier part of the inverter seems to be nfg. Any help with this would be appreciated. Are there typically user replaceable fuses, thermal overload relays in these units? Thanks, WC