Hi Victor,
Your ESC is the limiting factor here, unless you make it watercooled, which is quite easy.
I'm running this motor in a 50 cm raceboat:
http://www.hobbyking.com/hobbyking/store/__11875__ADS300_Water_cooled_Brushless_Outrunner_3000kv_300w.htmlOn 2S, turning a 36 mm surface piercing prop (roostertail), it runs about 30 mph and is a handful to control...
The very effective watercooling keeps the motor cold, the 40A ESC gets handwarm.
As your motor is even smaller, mounting it on a watercooled mount would cool it sufficiently to run it in a MTB style hull, provided you build as light as possible.
If your ESC is a flight type, with an aluminum plate over the Fets for cooling, adding watercooling is simple, using something like this:
Or if you have a drill press, make your own, fitting for your ESC:
There are a lot of (free) plans available, I'm currently working on this Italian M.A.S.:
I have the (simple) plan on my harddrive, so if you want a copy to scale down (mine is 43,3") to fit your motor/ESC combo let me know.
Regards, Jan.