i have a 9' pontoon boat and i use a minn kota with 52 pounds thrust, i am usually in rivers though, if your gonna be in a lake most the time i would use somewhere in a mid 30 to mid 40, whatever you can get away with using only one battery, the only problems i.ve had is being a little heavy in the back(because of gear+battery, for long trip)and having the battery stay in the right place, you'll be fine though