Sure a lot of variables there. I have the same trolling motor on the same boat with a 60hp Mercury. I am running 2 group 27 batteries. It is a pretty efficient motor. It would depend on how long you wanted to stay spot locked and gow hard it was having to work to keep you in place. At 50% power that trolling motor draws approximately 20 amp. A group 27 battery depending on brand shows to be rated at 80 to 100 amp hours. At 50% power it would run 4 to 5 hours depending on which battery. It is all tradeoffs. I am running 3 batteries 1 cranking and 2 trolling in that same size boat. I had looked into lithium for the trolling batteries they would save weight in the battery compartment and a fella's wallet. I would say on average you could get 3 to 4 hours running out of one battery. I have been out on days when the motor was running at 9 or 10 on spotlock to keep up with the current and wind. Other days it would run at 2 or 3 to maintain position. I went with 2 batteries to have the capacity to fish all day if they were biting good. Once the battery is getting depleted the voltage starts to drop down. That will cause the motor to pull more amps to do the same work. That produces more heat in the motor. On the scale on the trolling motor I rarely use the batteries down to 50%. They get plugged in a charged when I get home