3.0 or 4.3 mercruiser ?

[Entourage]

I cruise at 24 kts at 3800 rpms wot 4700 rpm 33 kts and do a 60 mile round trip with a charter of six with fish and burn about 30-35 gallons of fuel. Using mercury inertia 15 pitch stainless props. My friend has a older carburated 4.3 with the 4bbl carb and his fuel consumption isn't as good especially when he gets on it. I have a 20 ft safari and I was going to put a 4.3 in it just never did it. I know the engine compartment may be tight cause I did do some measuring.