Thanks to everyone who has chimed in so far. It sounds like I shouldn't expect the batteries to give me 14 hours of 2.2 mph?
How exactly do you use the Minn Kota for steering in conjunction with the gas motor for speed? I can set a bearing on the Minn Kota, but I would have to set some kind of target speed with that, right? I would think the Minn Kota would turn the boat sideways, working at cross purposes to the gas motor. Maybe the Minn Kota has to be set to a higher speed than the gas motor so it can pull in the same direction, at least a little? Then do you have to adust the gas motor speed as you turn in and out of the wind?