Do I need a kicker motor?

[roffey]

Do I need a kicker motor? I don't fish that much or if I do it's mostly just casting. The waters I plan on boating on are quite long, about 250 miles long but do have boat traffic. My boat is big enough that I would not be able paddle it. I have a single I/O. I was thinking of a 9.9 or 20 hp just to get me off the water if I smoked my motor but am thinking do I really need it?