I should add that according to the show I saw, the system is available for boats 38-53 feet long and costs 300-600K!
It is 30 % more efficient than a conventional stern drive (in output and consumption). They raced 2 identical boats, one with the new propulsion system, one with conventional and the conventional drive had a 250 hp advantage and the new Penta driven boat kicked it's ass and had a 50% smaller turning radius. The exhaust is vented out underwater into the wake, so no fumes either.
I feel we are on the cusp of some cool auto/aviation/marine technology within the next 3 years or so. There is more money being thrown at it than ever before.
JV