I think I need to add a 4th 12v battery and a power panel to the boat since I have one ciggy outlet and I have 3 things now (satellite radio, camcorder & bullet cam) to power as well as the sonar electronics on the boat. All the electronics run off the cranking battery, so I think the 4th battery is now necessary, takes some amps to crank that big motor over... For now I am going to see how the AA batteries work, their prices for the recharger were rather high, I thought.
That clamp loren linked to looks good, might have to get that too.