If it is of any help, it was the belt tensioner. The belt tensioner pulley was about to fall off. Temp and all else was normal, but the weak belt tensioner did not run the alternator and wore out my batteries.
I contacted Indmar awhile back with a oil/oil filter question. I asked if Rotella T5 15w40 is good to use and he said yes. He also gave me a list of oil filters. Ours is a 13 so I’m pretty sure it’s the same motor.