Exactly what I was thinking...

Yes, 225 hours worth, as it would appear - on this engine.

I'm thinking that for a given boat at a given weight to travel at a given speed will require "X" amount of power. If you can produce the same power at a lower RPM, prop up to keep the same speed/RPM relationship, and obtain a lower fuel flowrate as a result, how can this not result in reduced fuel consumption?

At what load and rpm ?

With the newer EFi engines that you can take a snapshot of engine hrs vs rpm, you'd be suprised how low of an rpm most engines are run at over there lifetime.

You surely can't believe headers will save you much at low rpm.

Also remember, math dictates 0 mph = 0mpg....no matter how effecient an engine is.

Heh Nauti -

You referred to this: http://custommarine.com/headerapps/dyno_data4.php

You do realize dyno graphs are at WOT don't you ?

Cruise is not at WOT.

Therefore, any fuel flow #'s you are using for your fuel efficiency question is thrown right out the window.

If you are hard up to buy the headers...go for it...it is your money. I would not fault you for it. Not really anyway...lol.A performance exhaust manifold (Eddie's or etc) will usually have more dependability.

If I where to spend $2500 on a SBC I'd get heads, cam, intake and carb. Crank that beatch right up.

I've never put headers on any engine (auto or marine) to get fuel mileage up. Every set of headers I've installed were always for sound and performance. Fuel efficiency is merely a dream at that point and I start praying that Al Gore and Ed Bagely Jr. both have heart attacks if they find out I've increased my carbon foot print yet again.

I did Stainless Marine manifolds on my Crownline last year. Way lighter than stock and the boat didn't pick up any RPM, so therefore no more power as I can tell. Interestingly enough I did notice lower water temperatures at idle even though my old manifolds were in excellent condition. I am hoping they will be more beneficial as I turn the wick up on this thing with a stroker motor in a couple of years.

I don't know how I could possibly qualify fuel savings unless I logged every hour on the boat and what I used it for. 2 hours of tubing uses more fuel than a day of cruising in this thing.

if you need manifolds anyway, Gil alum will save the same weight for 1100 or so. but they look like ugly stockers. if you wanna stand behind her and check out her hiney while she bends over to check out your race motor, then the EMI's or Gils or stainless marines might be the way to go. if you wanna save fuel, jam a big stick into the hole where the table goes and tie a bed sheet to it...

Headers can save you tons of fuel, so long as you don't start your engines. In theory, most of us install headers on our engines so that we can let them breathe better. Why do they need to breathe better? Because we just upgraded the cam for higher lift & more duration so we could get more of the fuel in & out of the combustion chambers that we upgraded by going to heads with bigger valves & ports so we could make a bigger explosion in the combustion chamber & make more of that horsepower thing that we need in order to spin the higher pitched props so we could go 5 mph faster if we're lucky. In the theory of engines, they make more power by making a bigger explosion, but to make that bigger explosion we have to have a bigger "charge" and engine just can't "eat" (intake) faster than they can "poop" (exhaust) which is the real reason that we put headers on our engines. That plus they look & sound good, and we can check out some choice tail when they're bending over looking at all the shiny stuff on our engines...

I fell for the bogus CMI claims on my old 496HO. After almost $4,000 I saw zero gain in top end, acceleration or any improvement whatsoever. At 2 MPG I wouldn't notice a slight change in fuel economy. This is not the activity to be concerned about gas mileage. Do the CMIs only if you are building up the entire engine, of course then you'll be burning more gas to make more power. . . . . . . . . .

[QUOTE=SB;4139729]
You do realize dyno graphs are at WOT don't you ?

Cruise is not at WOT.

[QUOTE]

Yes, of course I know this data is at WOT. I wish part-throttle data was easier to come by!