On Wed, 08 Nov 2006 11:36:48 -0500, DSK wrote:

We burn about 1 3/4 gph cruising about 7 to 7.5 knots. The
boat will (in theory) go 8.5 but fuel consumption starts
getting up into the 5gph range and we make a loke of wake
and foam and noise, for not a lot of speed gained.

Here's another data point:

On our Grand Banks 49 we average about 1 gallon per mile on extended
cruises unless we make a really concious effort to economize which can
save an additional 10 to 20%. That includes about 4 hours per day of
generator time, running on both engines, and using active stabilizers
virtually 100% of the time. Our average speed is about 8.5 kts,
slowing to about 7.9 if we are really trying to stretch the fuel.