Fuel consumption figures for Mercruiser marine engines:

3.0 L: 6gph at 3500 cruise, 11.5 gph WOT
4.3 L (2 bbl): 8.5 gph at 3500 cruise, 16.7 gph WOT
4.3 L MPI: 9.0 gph at 3500 cruise, 19.5 gph WOT
5.0L (2 bbl): 9.0 gph at 3000 (not 3500) cruise, 20.5gph WOT
5.0 L MPI: 10.9 gph at 3500 cruise, 22 gph WOT
350 Mag MPI: 12gph at 3500 cruise, 22gph at (5000 rpm) WOT
MX 6.2L MPI: 13.2 gph at 3500 cruise, 25.1 gph at 5200 WOT
496 Magnum: 16.0 gph at 3500 cruise, 30.5 gph at WOT
496 Magnum HO: 18.5 at 3500 cruise, 33gph at 5000 WOT.


Hmm, lets see: Running a pair of 496 HO gassers at well above cruise
speed would likely burn
close to 30 gph per side or 60gph total. 60 gph X $5/gal = $300 per
hour in fuel costs. Over $2000 for an all-day high speed run.

Running the same engines at 3500 rpm cruise would burn 37 gph, for a
total of $185 per hour in fuel costs at $5 a gallon. Still not cheap by
any stretch of the imagination, but at least not as far out of the
questiong for most folks as a $2000 daily (or even weekend) fuel bill
would be.