Have you checked your 12v system lately, humidity on the sailboat causes things to deteriorate a little faster. I noticed some white powder flake build up on one terminal and a little rust on the starter end. Also one of my Jeeps wouldn't start the other day, I hadn't driven it in a long time and had to clean the connections from the battery to the starter to get it to start. I hit everything with corrosion block and all is working well right now.