One of my current type 31 batteries is no longer holding a charge. I think it is time to replace both of them. What is the best battery I can get for running two batteries in parallel for a 12 volt Terrova. I have both batteries installed under the console, and I have several inches of wiggle room. I had to put them there because there was not room for two type 31's and a cranking battery and a charger and two water pumps in my mechanical compartment at the back. I could fit two smaller tm batteries back there if they gave equal staying power, and if this is possible it is what I would like to do. I am selling this boat this fall and I think folks would prefer the tm batteries being where they are supposed to be. Boat is a PolarKraft 176ff Bass America ........ What would you go with?