You're right of course about the exhaust allowing you to push more air through..... i didn't expirience a lean burn situation on my motor.... but I don't understand why the timing would be affected?

I put Imco Powerflows on my t/330's and picked up about 2 MPH and a few hundred rpm ...can't remember exactly after all I've slept since then

Most of our customers have seen a 2 to 5mph gain depending on the package.

Don B.

[QUOTE]most of these aftermarket companies do little or no actual testing on a boat, be careful.


IMCO does extensive testing on thier equipment, both on dynos and in boats. they are also very helpful when in the middle of a project and you get stuck.

Tyler Crocket has a lot of info on dyno tests on most aftermarket exhaust Chuck. Give him a call.

And you don't have an efi motor, so why do you care???

Saber28, well said.

I have the Powerflow Plus headers on one of my 41's. The engines are tall deck,600inch, 685hp naturals. big,dumb,5100 rpm engines. 685hp with car headers on the Chief Engines dyno,680hp with the Powerflows on the same dyno. I had Stellings that were not repairable and spent $7500. between the headers and Stainless Marine-installed tailpipes for the short stagger. I feel like there is no difference between the two. the PP Plus headers have much longer primary and secondary runners. They are also around 3 7/8 exhaust diameter compared to the 4" exhaust size of the Stellings.

We run a P boat " Wazzup" 556cu.in. 730 hp. at 7200 rpm no power loss on Power flow and no dam leaks

Dennis Moore has address this a little in his book. Some of these manifolds have better primary designs than others and some have only a 2.5 inch collector even though they a 4" hose going out through the transom. Its weakest link of restricted flow is still the 2.5 inch collector.

Anyone ever here using/testing the new Stellings manifold design? I think it's a couple of years old...you can even get them with 5" tailpipes. I know Doctor Dave is running them on his Cig with blower engines. I wonder how they stack up to the tubular headers?

The KE's sound interesting as well.

KE's all the way, they are just LOUD and $$, But have run mine 4+ yrs. in the salt water and they are still doing great. I put shotguns mufflers and that seem to help quiet them down a bit!
BTW, they are on an KE tuned HP500
Hope this helps,
MD