I currently have a 5 HP 4 Stroke which works great for trolling etc....
However here is a solution if you really like to up the HP for whatever reasons..
http://www.bobsmachine.com/Products/...ate_kicker.cfm
Hydraulic Kicker Jack Plate - Rated to 40HP
With a maximum engine rating of 40 hp, BMS's hydraulic kickerjackplate provides slow-speed power for cruisers, auxiliary power for sailboats and trolling power for fishermen.