On Mon, 29 Jun 2009 11:28:01 -0700 (PDT), Frogwatch
wrote:

From what I can determine, once a boat is on plane, it is primarily
the weight that determines fuel efficiency so a lighter weight boat
should give much better fuel economy.

Power required for a given speed is directly proportional to weight,
for both displacement and planing vessels. Power required varies with
the cube of speed. Mileage varies with the square of speed.

Casady