means the reg/rectifier is charging your battery.
When you did your good deed, was your motor running or did the other boater just hook up to your battery (your engine off). And if running, when did you have problems? It sounds like your motor shut down, you replaced a fuse or fuses and motored on -- then had issues later(?) Anything is possible, but doesn't seem like that episode would affect your keyswitch -- which you can test with a continuity tester, btw (engine off and battery disconnected).