I just bought an 11' Sevylor Inflatable Raft to use as a tender for my boat. You can put up to a 3.5 hp motor on it. I was looking at the electric trolling motors and was wondering what would be a good one. Would 30 lbs of thrust be enough to move this around (it's 11' long, weighs about 40 lbs)? What about shaft length? I don't need anything fancy, just something that will get me around so I do not have to paddle!