Exhaust

[BrendellaJet]

Question-Why is it that a lot of the blower motored boats use Zoomies, and not the NA motors? Are they much louder than OT headers?

[Tom Foolery]

I would guess that it has something to do with exhaust scavanging. On a blower the benefits of exhaust scavanging are probably eliminated by the air/feul being pushed in by the blower.
This is just a guess but it seams resonable.

[flat broke]

Brendella,
TomFoolery hit it on the head with the scavenging effects of a collector on a header. NA motors rely on the negative pressure from the exaust leaving the cyinder to help draw in the new intake charge. A properly sized and constructed header with the appropriate collector will assis this process better than zoomies.
As far as loud. I think that is determined more off of final CR than the fact that there is a blower on top the heads. A high CR motor will be louder at idle than a blower deal for this very reason.
With what you're shooting for, you will be looking at headers for your application.
Chris

[HOSS]

Are zoomies louder. Run them and see why you hate to ride in your boat for more than 15 min runs. And don`t bother with more than 2 seats. Both will be filled but thats it.

[Jim Brock]

My motor is NA put on zoomies and ran my quickest and fastest time ever 8.60 et and 125.50 a 480 cu. in chevy headed motor, If you have the right application they will work. Jim Brock MJ 460

[BrendellaJet]

anyone care to define the right application? I was going to buy a set of lemons headers, but I like the look of the zoomies...