Austin -
Woody's got a good handle on it. Check out your local Academy. They should have either Nissans or Mercs. No one there knows much about them, but their prices aren't bad. Just make sure you get THE RIGHT-SIZED WHEEL for what you want your boat to do!
I've had a 40 Merc 4S for almost two years now, and after I finally got THE RIGHT-SIZED WHEEL for it, I love it. I do send it back to the dealer in the fall for maintenance and oil changes - I've been doing all that myself for tooooo long to keep at it. Anyway, you'd almost certainly like a 20 - got a feeling a 15 might not have enough umph.
Whatever, bon chance.
Pete