IMO buy as much thrust as you can possibly afford. You might not need it all the time, but when you do you will be glad you have it.
BPS sells the Minn Kota Endura series. You can get the 45lb thrust for $219. You can get a walmart battery for about $100. Thats $319 and you will be glad you bought what you bought.
thanks guys! after reading your responses i think im going to go with a 50# minn kota on a 36" shaft. I was probably off on my guess of the canoe length, its probably more like a 15'. the 50# might be a bit big but i wanna grab a small john boat this winter and dont wanna have to upgrade to a larger motor if i only went with say a 30#. also after reading some other posts i am going to buy 2 batteries, just in case lol.
out of curiosity has anyone used/heard about the BPS brand motors?