For what it is worth. Go with the biggest battery that will fit in the boat. Put it in a battery box. I am planning a Group 31 deep cycle in a battery box I purchased at Walmart. The box comes with a strap and screw down strap fittings. Keeps all the crap away from the battery. Get the battery with bolts on top instead of the tapered lugs. Be sure to solder the terminals on the wire. Cover the ends with heat shrink tubing. Use the spray can corrosion control to protect the lugs and wiring terminals. Less problems. Most big rigs and golf carts have that system, Rigs don't like sitting idle because the lights do not work. I plan on a small solar panel to keep the battery up. Keep a box of Arm & Hammer to neutralize the inevitable spills. Hope this is helpful, Ken