inverter by plugging into an outlet that is protected by GIF. You are ending up with two GIF protected outlet plugs in series. It sounds like this is a new problem. It seems that you need to isolate the problem to either the outlet in the boat or the inverter outlet. I would bypass the outlet in the boat by plugging the inverter into shore power with an extension cord right to the dock outlet so you are dealing with only one GIF and see what happens. If it works then I would look at replacing the GIF in the boat outlet. If you have the same problem then I would start looking at the inverter GIF. Good Luck