A lot depends on how that hp is made.

an 800hp engine with an efficient blower like a whipple and a perfectly tuned EFI setup will get way better mpg than an 800hp with a big old fashioned roots blower and a couple Holley dominators.
Then again it will cost a lot more up front so comes down to when/where are you gonna spend the green.
:)

Johnathon,where's my book?

Absolutely save $$ at identical MPH between engine running 4000 rpm and one running 3000 rpm. Need big difference in HP to work because the 3000 rpm big engine will burn more fuel than 3000 rpm small engine. With the difference you state, should actually save fuel if cruise speed is same. I stepped up from 260 HP to 450 HP in an 18 ft boat, cruise speed 30 mph for both and the 260 was turning 3200 and the 450 hp with big pitch prop ran 2200, secondaries were not open. But I also propped for max cruise so it didn't pull past 5200 rpm, but that was too fast for an 18 ft tank, for chine walking.


As this is a very, very low priority for us, the new twin rig has one new 540/600 and one old but still serviceable 454/330, to run it like this requires that I match Rpms so the 540 burns more fuel than the 454, but when the 454 finally is replaced (end of this summer), will step up the wheel pitch and expect fuel consumption to decrease below 454 usage when running at 30 to 35 mph, our "comfortable" cruise speed. Of course, if alone, or with the like minded guys, the "comfortable" cruise speed increases about 40 mph ;).

wow,double wow.You have a 600hp 540 on one side and a 330hp 454 on the other?I can't imagine that.Thinking,no i still can't.

So will the bigger motors use more fuel than the smaller at the same given speed??

never mind

What does that mean?