Back. I found the problem on the boat.
I blame my old man, that's all his creation. Turns out I connected the front battery backwards. After I'd eliminated everything else, I took a real close look at the batteries. The leads to the front battery are fucked up. The positive wire has black electrical tape for several inches after the lug. The lug on the negative wire is painted with red liquid electrical tape. Being that I was reaching into a hatch to connect it up, I couldn't see far enough up the leads to see what they really were :grrr
Let's just hope that nothing got fucked up, and if I did fuck something up, it's just one battery :wait