Consider weight of boat, where you fish, how you fish, and if you have a kicker. Had 36 on previous two boats but went to 24 on 1875 Impact I have now. I fish the Miss R sometimes strong current and get by fine with two ā31ā AGMs. For 6 hrs trolling or more I use kicker for 60 to 75 percent of thrust and TM to steer. 36 adds a lot of weight and cost for TM, on board charger, and batteries. On a 20ft. Glass Iād lean towards the 36 to cover all bases.