Re: batterey size
1) Deep Cycle
2) Group size 24 minimum (27 prefered)
3) Check RC (Reserve Capacity) specified in minutes. XXX@23 amps. Bigger number means longer run time.
4) What you need depends on how long you are out at a time. If you fish for a couple hours and head back a group 24 may work fine. If you are out for 4 - 5 hours and spend most of that time slow trolling or using the motor alot you need a group 27.
5) You need a smart battery charger to charge the battery immediately after each use.