http://www.marineturbine.com/technical.asp
These guys make a turbine outboard motor that produces 320hp, 425ft/lbs of torque, and weighs only 220lbs.
The nice thing about this motor is that "it'll run on diesel, kerosene, jet fuels, or any combustible gas or liquid".
http://www.marineturbine.com/press/t...oats022001.pdf