simple boat design 8-10ft

also,if the caging isnt strong enough,the craft could get squashed if it hits it at high speed.

 

i like working with wood,personally,its easy to piece together,no chemicals involved,great flexibility,looks fab and can be quite light,but i dont know how safe it would be for an open (whats the rear called in boating terms?)craft (oh and dont take much from me,im only onto my first boat).

 

also,again consider the hull type, a trimaran is probably the fastest and most efficcient,but try and make it a flat bottomed trimaran or rounded bottemed.

 

As to the driveline: Trying to develop a new propulsion system is best accomplished by starting with a known good boat. Working on a new boat simultaneously will almost guarantee trouble. And given the current state-of-the-art in waterjet work, I doubt you'll be able to improve on it much without significantly more resources than you likely have at hand.
As to the boat: The roll-cage thing works great for cars, but for boats it creates hard-spots against the hull that are prone to failure. Look at how a jet-ski is built for inspiration on this count, or look at a high-performance jetboat like NT's Squirt testbed hulls http://www.gas-turbines.com/squirt_2.htm .