22v Fuel Consumption Question

[dreddy]

I'm looking seriously at a 22v that has the Marine Power 6 ltr. engine. I've bought a fair amount of fuel for my friend's 22v with the 5.7 so I know that they are relatively fuel efficient boats (especially compared to my MC that had the 6 ltr.) but will the larger engine use more fuel/hour in typical wakeboarding and surfing use? Many people have indicated that the larger engines actually use less fuel. I've read this often in the MC forums where the 8.1 uses less fuel than the 6.0 in their big boats. Is the 6.0 engine just a gas hog in any application?

I'd appreciate any thought or experiences that you may have

Thanks in advance.

[whitlock87]

I got this from boat test

[Wakeman22]

I got this from boat test

Nice chart. says it all.

[talltigeguy]

If I am reading that right, with both boats at 3000 RPM, the 409 uses 7.1 GPH, and the 343 uses 6.4 GPH.

With the same tranny and the same prop, and same boat, I think you need to have identical number of revolutions of the propeller to make the boat go the same speed, right? And in these boats, there is no slippage, so 3000RPM means the same number of prop rotations in both boats. So unless you can prop the 409 better, you have more fuel consumption with the 409, albeit a modest increase.

Somebody educate me a little on this one.

Having owned a Mastercraft with the 8.1, and a Malibu with the 6.2, I don't see any real difference in fuel consumption until the boat is massively loaded. The 8.1 shined when I had massive amounts of weight in it. It never groaned, it just accellerated no matter what. My Malibu on the other hand, seems to struggle when I have far more than stock ballast. It took more gas to get the 8.1 to get on plane faster. I guess simple physics tell me that it takes more energy to get on plane faster with more weight.

Just rambling here....

Now the 5.7 in my Tige on the other hand, was much more fuel efficient, but I don't know if I ever would have gotten on plane with the sorts of ballast I have in the other boats...right now I can't even remember what prop I had on that thing...It might have still been the 537, so that could explain a lot.

[dreddy]

Thanks for the tables. It helps a lot to see some comp data.

Just as the prev post mentions, it doesn't account for prop differences however. I would assume that the data in the tables accounts for "optimal" propping for the torque available.

Thanks

[sawyer1206]

On my ACME 537 with 1500# ballast and 800 passenger we were getting 7 to 8 GPH. With the 1235 it looks like we are around 6GPH with the PCM Excalibur 330 5.7l.

[dreddy]

Interesting... I just looked up the specs on those props:

537 - 13.5 x 16 x .105
1235 - 14.5 x 14.25 x .105

Seems that the 1235 is more of the "power prop". I would have expected higher fuel usage for it but maybe all of that extra diameter makes more of a difference than the smaller pitch.

Maybe having the perfect prop is more important than the big engine for a 22v.