Here's a list of GPH I recorded in a 22' Stoker with a 502/500HP with 5 people aboard:

That's as far as I went. From there up, it was already tuned for 12.8-13.0 air/fuel.

The rule of thumb I use is 1 GPH per 10hp.

Whenever this topic comes up people always say that gas is the cheapest part of boating, etc. Sure, that's true. But there is nothing wrong with analyzing fuel consumption for a few reasons.

Having a ballpark idea of how much fuel a boat uses BEFORE buying it is a good idea.

NOT running out of gas. Gas guages aren't very accurate. Some don't buy the GPH thing, but when I went to the gas station, I could look at my hr. meter and know within a few gallons how much to fill.

Determiing optimal cruising speeds.

Smartcraft or Diacom software is great for these purposes.

what about going slow thru no wake zones.. what should I achieve with the following set-ups?

Baja 272 with 502
Fountain 35' with twin 496, 500, or 502
Fountain 38' with twin 496, 500, or 502
Fountain 42' with twin 496, 500, or 502

Smartcraft or Diacom software is great for these purposes. [/QUOTE]

Add one more to dave m's list. Lowrance also has chartplotters and gauges compatible with their fuel flow senders for instant gph, mpg, fuel remaining, fuel used, etc

Now would this be heading into the wind or with a cross wind?

I want to make sure my calculations are correct.

Outboards use 10% of h.p. @ WOT... 300 h.p. = 30 gph @ WOT "HIGH LIFE"