When looking at the same boat. think the crusing MPG would be much different?

like if you had a Formula 382, with 502's vs same boat with blue 500;s

i know at WOT the blue would use more casue its making more power, and that takes fuel. BUT what about at 3300 rpm cruse? would the difference even be noticable?

Probably not. And you may not be happy with a 502 equipped 382 as the top speed is likely to be less than 70 and it could actually use more fuel to cruise at 55 mph.

+1

Funny thing is for all my years of go fast boats people with cruisers always commented that they would not want to put gas in it. This year I purchased a cruiser (mistake ) and realized that a single BBC uses just as much gas to cruise from point a to point b as my friends 388 hustler with twin blown 500hps. How is this possible? First he cruises at 60, and the boat is out of the water and hardly working. I am cruising at 30 mph and working hard to keep the pig out of the water. I have to run twice as long to get to the same place. We truely use the same amount of fuel, pretty sad.

I would guess that you would hardly notice a difference in MPG even at WOT.

thats what i was thinking. just checking my thought.

At the same rpms, the 500efi's will use a little more fuel, but they willl also be making more power. The 500efi's will also be spinning a prop that is probably 2" more pitch and the cruise speed will be a few mph faster. The actual MPG should be pretty close.

I once ran a 1990 doral prestacia cruiser with 2 x 4.3 to point a to point b. ran the same trip with my ex formula 35-7 with 2 x 454 /480 hp, and whatever the mpg was, total cost for this trip was the same in gas !

no replacement for displacement!

I switched from 502 EFi engines to HP500EFI engines and the fuel consumption was almost equal. I never did go to a larger prop which may have actually increased fuel mleage. Real difference was that the boat could only reach 4700-4800 rpms at WOT with the black motors and sailed past the rev limiter with the Blue motors (5250). So I probably could have used at least another 2 inches in pitch.

same here...did the rideau canal with my sunseeker w/twin 454 mag and my friend with his 26ft doral,single 350...at the end of the week,he had burned 100 dollars more fuel than me...

Years ago Hot Boat did an article where they took a boat and started with a V6 and tested it's performance and fuel economy. Then did the same with a 350 SBC then a 454. As they went up in power they repitched the boats accordingly. The bigger the motor the better the economy and of course the cruise speed increased. They then went one step further in another test and added a blower to the 454. It got even better fuel economy. This is the story I tell my wife when she's asking why I'm working on the motor again! I'm just trying to get the boat to do a 100 so we get better fuel economy while were cruising.

Outstanding logic!