4.3's Fuel Economy advantage

[Craig]

Hi guys -- I know this has been kicked around some before, but a friend of mine is considering a boat purchase and, considering fuel economy, was even looking at little 3.0 four bangers.
Looked at a 90's Welkraft 190 this weekend with him and after we saw the 3.0 Mercruiser idling on it's wobbly single front engine mount, (and for some other reasons) he decided to pass.
He's now considering a 4.3 and we were dicussing fuel consumption advantages over a 5.0.
I figured since the Donzi 16 is (or has been) available with the 4.3 (6 cyl.) or 5.0 (8 Cyl.), this would be a good place to get some feedback. Does anybody have some gallons per hour data on the 4.3 equipped Sweet 16 vs the 5.0 equipped one?
Appreciate any help along those lines.

[Craig]

I've heard the 4.3's are better in every way?

[mikev]

not sure about comparing the two but in my 19' Ragazza with a 4.3 I can run all day playing around tubing and stuff on about 20-25 gallons of fuel unless I get into the 4bbl. alot which for me kicks in at 3400 rpms so i cruise at 3200.

[Craig]

What is the 4.3's rated HP with the 4 bbl?

[mikev]

190 hp unless its a vortec then 220 mine is non vortech but edelbrock says 18+ hp over stock so at 208 supposedly :wink: i also am running a 1" plastic spacer for a little more low end power and i can feel the difference but then again i went from a 175hp 2bbl setup.

[Craig]

Thanks Mike - That gives me some idea that, as expected, the 4.3 is not as thirsty as some set ups.
I was thinking maybe with the large amount of 16's with both 4.3's and 5.0's I could get some feed back on the subject. Same boat, same drive, different motor.
I know the power to weight ratio has been discussed here and some have said the 4.3 in the 16 is a desireable set up due to that.

[22billyzx]

I went from a 19 ft Thompson...170 hp 4cyl to the 22 ZX I purchased this spring. 454 non mag EFI,and i am thrilled with the fuel effeciency of this motor. It`s nice to have the extra horsepower when ya want it!

[Craig]

What I think my friend is specifically wanting to know is: Is there a significant (or any) fuel efficiency advantage to the 4.3L 6cyl. engine over a similar boat with a small block 8 cyl.