How old are the batteries?
Some more things to check. Alternator belt, is it worn or loose? The batteries on my 272 are in the cockpit lazarette. If I remember correctly they are located in the cabin somewhere on the LE model. Are the cables clean and intact? If you have an off/1/both/2 battery switch and leave it on both when you are away from the boat, it is likely that the weaker battery will draw the current from the better one and eventually drain both batteries.I had that problem for two seasons before I found out what was wrong and configured a system recommended in the WM catalog using three on/off switches and a battery combiner. I also replaced both batteries, the house deep cycle last season and the starting battery this season. No problems. I have no shore power at the slip, so all of the battery charging is done by the Mitsubishi alternator. I should add that I operate minimal 12V equipment on board. I am not a gadget nut...You will find some interesting posts in the archives which discuss the alternator question. I'll check for you and if I find something useful, post another reply.Tom