Thanks for all the feedback. I will check the dock receptacle. Everything was fine for 5 years until late summer. Does anyone know where I can get a panel for the boat if it is bad? My panel measures 4.5" x 7". The opening is 4" x 5.75".
Blue Seas makes many sizes of AC panels.
They also have a description of the Reverse Polarity indicator.
Looking at the circuit it is just a LED diode(with internel resistor) between the ground and neutral. If there is a difference of voltage then the LED lights.
If the LED lights, the LED isn't bad. So there has to be a wiring problem. There is nothing to "go bad" in the panel to cause it to light.
The panel is just circiut breakers and wire and the indicators. There's no guarantee buying a $250 panel is going to fix anything
The Neutral and Ground are tied together in the marina's main panel. There should be 0volts between them.
If the ground on your boat is not connected at all to the marina ground it is
possible to light the LED. Your boat has a galvanic isolator. if that is bad you
could get that symptom.
You can find the way to test a galvanic isolator on the web...probably on the blue seas site...