I have run a 4hp Merc, a 6hp Yam, and a 9.9 Yam on my 22. I have a motor mount that allows dropping the kicker about 4-6in below the mounting point on the transom.
The 4hp Merc could push the boat 2-4mph in calm water, the 6Yam about 4-5. The 9.9 Yam does 6-8mph on my initial testing.
The drop...