I noticed my 140's battery died a couple of times for no apprent reason, also half my running lights go out when it rains(???), anyway I tightened the alternator belt,I used a short broom handle and carefully wedged it between the block and alternator, avoiding using the coolant pipe for leverage, only the block, this allowed enough force to be applied to tighten the belt properly, not to tight though that will put excess wear on the component bearings. Apparently the belt was silently slipping, alternator not charging the battery, for some unknown reason the light didn't illuminate, maybe there was just enough voltage to keep it out.