What engines do you have? Look in your manual to make sure the batteries you are choosing meet the motor requirements. Yamaha's need a battery with 182 reserve minutes, along with the 512 CCA minimum requirement.
I have had excellentservice from my Deka lead/acid batteries. They also make Gel Cell (Don't buy this type) and AGM's (Great, but $$$).
Here's the DEKA Spec Sheet link.
http://www.eastpenn-deka.com/assets/base/0194.pdf
I use the group 27 starting battery for the motors and a group 31 Deep Cycle for the electronics and accessories.