There's so many variables in this question, it's almost impossible to answer. I can cruise "sensibly" at around 2800rpms and get decent gallons per hour. However, if I take em up to 5000rpms, I'm thinking I get almost 30 FEET per gallon!! Not sure if the 496 is "efficient", but sure beats rowing......

Max mpg plained off. Aka most efficient cruise speed. Like how boating mag reports.

Merc 1100s. They are turned down 1350s that come with 6s. Cig is only building new boats with merc power.

My 28 Velocity with a 496 gets 3-3+mpg cruising at 3500rpm and about 2mpg at wot.

According to all the information on the 496 I could find it is most fuel efficient at 3500 (if you call it efficient :) )

Mine is pretty good, for a performance boat. 33 Eliminator with box stock 500 EFI. Light boat and fuel injection!

Hogie is correct on the Merc 1100's but my friend's boat has the #8 drives.
It was originally the Ducati boat that was bought at the show by its first owner who didn't like the plain paint and he changed the whole boat to a blue, silver and pearl white.

Sounds like my previous boat, 24 Superboat w/496HO. According to the Diacom scans I ran, I was burning 12-14 GPH @3500 RPM. At 3500RPM I was running about 55 MPH. So, that averages roughly 4 MPG.

That's what my research showed, 14gph at 3500. My boat runs 48mph at 3500 with a 26 bravo prop.

What prop were you running to get 55mph at 3500, a 28 bravo?

Nice. Those fast singles are where it's at.

Yup, 28P Bravo