Doesn't it just boil down to hull efficiency, weight, and water conditions? The horsepower needed to move these factors at your desired speed determines the mileage. For basic discussion a 350hp outboard, 496, 454, 502, whatever will burn the same amount of fuel when producing 300hp. So isn't it just a mathematic calculation?

Small cat 28'-32' with mild efi power would probably be best.

Not exactly. You're implying that all of those engines would have the same bsfc while producing 300hp, which is not the case. Pumping losses can be a problem at part throttle. The most effecient scenario would be to have an engine at wot but lugged down to its peak torque rpm and therefore at max bsfc. This isn't exactly possible due to prop sizing etc. The later generation suzukis have wideband O2 sensors implemented into the engine controls so they can lean out at cruise speed, this would be the optimal scenario for a gas engine. Other than that hull efficiency, weight and waves are the major contributors.

Nice of cig to give their clients so many options= fail

Is Suzuki the only manufacturer doing this? Thx rm

I don't know. There seems to be strong competition in the OB space right now and the guys on THT talk about efficiency as much of more than power and speed.