2003 Sundancer 240 5.0 mpi Alternator? - Last weekend I took one of my batteries out to change it and went on a 1 hour ride with one battery. My radio did not work so on the way back (another hour) I put the battery selector to both so it powered the radio. When I returned to dock I smelt some burning rubber in engine compartment. I installed a new battery and went out yesterday. The volt meter stayed at 13 (usually runs at 15 or 16). The temp gauge showed 140 when it usually shows 170. I then got a long beep while getting up on plane. SmartCraft threw a few codes (fuel gauge, trim gauge ) I switched to other battery and did not get the beep or any other codes. While anchored, I switched back to other battery and it did die after a few hours of radio, water pump, etc. no issues on way back with good battery (other than volt meter showing 12.5 volts. Did I burn out my alternator? How can I test it? Thanks