I plan to purchase another classic Lund S-14 Fishing boat to be powered only by Electric Trolling Motor. I have powered one in the past with a 36 or 40 lb thrust Minnkota Endura ( Think it was a 40) and was sufficient for getting around in general. Now, I plan to troll at the same speeds the Merc did but with what transom mount Minnkota? Would a 55 lb thrust be enough or go all out for a 70 or possibly 80 lb thrust 24 volt system. Also, with the maximiser system on the premium Minnkota's, would there be a need for 2 extra back up batteries to get through a long day of fitchin? I'm guessing the 55 lb may do the job and that would be easier on the pocket book but i am willing to spend the extra money if needed.
You're on the right track! A 55 thrust would probably do it in a 14 footer but a 65 would give you a bit more power which can help out on those windy days! I'd probably go 55 and put the money into some decent batteries. I went with a 24 volt system and 2 group 29 Interstate Batteries. I am amazed at the run time I get out of that setup. If you have the room I'd go with at least group 27 "size" on Batteries whether you go 12 or 24 volt!
Good Luck and keep us posted on how things go for you!