If I can put in my 2 cents:
I would go with a 2.5 HP (get 4 stroke for easy maintenance), all you need if you just planing in using in getting it in and out of the harbor. But if you plan to go further distance, may want to go bigger.
I have a Cal 21 w/ a 9.9 HP, way too much power and way too much weight, that's why I am selling it and getting a 2 or 2.5 HP.
My 2 cents.....LOL.