Along with the oars, I reccomend carrying common replacement parts on the boat. I always have shear pins, an extra prop, and extra speed control switch with me. It is easier to swap out easy stuff on the water than it is to row.
Check out the group 29 interstates. Plenty of reserve capacity. I run a 55 traxxis along with a fishfinder off of mine with no issues at all. I have enough juice to be out for 6-8 hours as long as I am not continually trolling.