I used to have a Ranger 1850 reata with a terrova 80lbs thrust. I could go all day trolling in heavy winds/waves on erie (10-12+ hrs) on two batteries with 3-4 guys on the boat. Buying good batteries and a decent charger is the key, I used the diehard platinium http://www.sears.com/diehard-platinum-marine-battery-group-size-31m-price/p-02850131000P Well worth the money. Plus you will keep a lot of hours off your big motor and save on gas/oil.
Nick