Too may variables to give you any great detail but here's a sampling.
I have an 07 with twin Honda 50s (BTW I think there ought to be a forum just for twins).
My log says about 1.7 GPH or about 5-6 mpg.
I'm a cruiser and spend two and three days out at a time mostly in calm seas. I like to cruise about 17-20 kts depending on conditions. I'd say I load moderately heavy.
I have OEM props 11.25 by 13 three blades and run between 2800 and 3200 RPM. WOT (80% of mfg suggested top RPM) on glass is 30kts by GPS.
In storm conditions with trailing seas I've seen 3.0 GPH.
I have ordered permatrims as others have reported improvements in efficiency in the RPM ranges I'm cruising. I'm really hoping to get some more control over trailing seas as often happens in the Channel on the way back from the West end of Catalina.
I'll let you know when I get the results.
In any case you have fuel to spare over a Grady White or other V-bottom.
Congratualations on the new boat...you'll love it.
