The easiest solution is to get a high quality alternator, (not one from autozone the rebuilders I have talked to will not touch a autozone rebuild, they say the components are junk) and take it to a local rebuilder tell him you sometimes get it wet. They can waterproof some of the internal components to make it last longer. when I was having this problem years ago I made a alt bracket for lil Suzy to attach a high amp GM single wire and I have not had to replace it since. Trail Tough sells the bracket for the conversion now.