"Dave Stadt" wrote

The key is speed. A boat runs most efficiently at "hull speed" which is
a function of length. If you want to push the hull faster than that,
fuel consumption goes up ridiculously, even worse than with airplanes.

True, and it is the rare stink-pot that goes at hull speed. g That is why
they have big engines; go fast and make noise, while burning lots of
hydrocarbons. ;-)

Only true when talking about displacement hulls. Has nothing to do with
planing hulls which include the vast majority of power boats. Planing
hulls
burn a tremendous amount of fuel untill they reach planing speed.

With the type of Great Lakes cruiser, or ocean cruiser that we are talking
about, having two 350 V-8's, most are semi-planing displacement hulls. They
do get up on plane to a degree, but there is still a lot of displacement
going on.

Most run at around 55% power, so that still comes out to a lot of gas for
two 275 HP (or more) motors.

The saying goes, that if you have to ask how much gas they burn, you can't
afford owning them. Lots of truth, there.
--
Jim in NC