What do you guys feel is the minimum thrust I could use on a 17ft fiberglass hull boat. I won't use it much, but I am definately getting one and have no clue what 40lbs or 55lbs can do. I am mainly getting one so I'm not completely 'up a creek' if the outboard goes south...that and if I want to put it in a pond (which won't be very often at all, the boat is too big for it anyway)

Thanks.