Hi All Hoping someone can help. So my 280/315 has 3 batteries. 2 starting and 1 house. Starboard engine and battery run alone. The port engine starting battery (new) keeps going flat when overnighting and luckily I have the switch to bank over and start the port engine after I have started the starboard engine. Now the port battery charges after running the boat. 65amps per hour on the V6 mercruiser. SO WHAT IS THE HOUSE BATTETY DOING??? it’s new also. Deep cycle 120amps. I don’t have the luxury on leaving on shore power. Can someone please advise? Thanks in advance.