Is extension cord too long or too small of gauge?

Did the charger get wet?

Anyone had any issues with their boat tripping a GFCI in their garage? My boat isn't plugged into the GFCI but there is one on the circuit that it trips, boat doesn't change, garage doesn't open, frustrating. The boat is a 2018 FX20 for reference.

If possible take out the GFCI and replace it with a regular 120V house plug, if you live in town most likely the city code will not let you take it out so if that's the case try changing it out and make sure nothing is wet or has moisture and that your plug on the charger is in good shape . If you can change it out the only problem will be is that the other plugs that feed off the load side of the GFCI will not be protected by GFCI anymore most of them may be outside or even Kitchen plugs.. The GFIC is very sensitive on ground faults so the slightest indication it trips, could be a weak GFCI or it could be detecting a slight fault most of all the items we use around the house will at some point especially when they get old cause the GFCI to trip I learned the hard./Messy way on my freezer in my garage it tripped and we did not realize it till about 3 -4 days later when the smell hit us after that I changed it out to regular plug and ran a new circuit to panel. I also had a GFCI plug in the shed where i parked my boat and a while back it tripped did not know this till i plugged something into that plug and no power, glad I was not going fishing for batteries were not charged so i replaced it with a regular plug. Open the compartment and let it get some air and if possible sun light if there is moisture it will dry it out then plug it back up to GFCI if it holds you know its Moisture/Wet if not then look at changing GFCI.

Is extension cord too long or too small of gauge?

Replace with a new GFCI. They get weak over time

This is very bad advice. And I’ve done it before. And I knew better. Before doing this, get the bilge as dry as powder and make sure the charger is dry as well. Check underneath the charger too for a puddle. Once dry, if it continues to trip the GFCI, replace it with an expensive top of the line 20 amp GFCI outlet. That usually fixes it. If it continues to trip after all this, be thankful it protected you because you have a ground fault.