But when you get trip problems as you describe, there is either a problem at the panel ashore or in your boat or in the cord you run. Finding that problem is important when it's consistent. I ain't no 'lectrician but as a homeowner that does his own wiring, if a breaker starts breaking I worry. Testers might help or else you gotta inspect your cord carefully, change where you plug in ashore and see if that makes a difference, then replace your breaker. At least that's the way I'd check the situation.