More properly called a "surface piercing prop". Common in the racing world.
Does allow the boat to go faster. Seems like that would improve "mileage"
as well but don't know.

"Richard Casady" wrote in message
...
On Wed, 20 Aug 2008 02:15:03 GMT, Short Wave Sportfishing
wrote:

It's an interesting design, but I'm confused about the tunnel system.
Looking at the drawing, it would appear that the prop sits half way
out of the water.

Than can't be very efficient.

Of course it can. Ever hear of an Arneson Drive. Only half the seven
blade prop is in the water. No drag from shaft, strut, prop hub.

Casady