MER Performance

So, Primary runner length, header size, has nothing to do with scavenging exhaust gasses or either the engineering; which = cost.

MER Performance

Here's a technical article, that will explain the importance of exhaust flow and scavenging. If you have a stock engine and want to improve the performance, moving up to a better manifold, with the same style runners, I could see. Taking a 525 EFI and changing header design to a short style manifold is going to effect performance and combustion chamber temps.
When spending money on a engine and wanting to not leave performance on the table, you better have the proper exhaust. It doesn't matter if you have a twin engine boat running over 1000 hp or a small block making 500+ in a single engine boat.


http://www.epi-eng.com/piston_engine...technology.htm

302Sport

I've heard the SM make the same or more power on the dyno, have you or any other engine builders tried back to back tests?

But hey your and engine builder so, the more leaky CMI's the better for you.

Wildman_grafix

^^^^^^^^ that is what I would like to see, some real dyno tests one with CMI one with SM.

I always was taught on a NA motor it's pretty Important.

MER Performance

That; I can't verify. I haven't done back to back. If I'am not mistaken SM offers a stock replacement and the Dominator Line. Take SM top one and compare it to Keith Eickerts, cast alum exhaust, those runners converge at about 15-16", those are great manifolds.
What I am hearing from this thread is; the CMIs are all about bling, they don't hold up and you don't need a properly designed exhaust, unless you have over a $300k boat. NOT TRUE

Looks like you have 2 nice boats, according to this thread; you could take either a couple of 55gal barrels or trash cans and cut the ends off and weld them together for an exhaust for your turbine boat.LOL!!!

302Sport

Hahah that's pretty true

MER Performance

Here's a easy way; not all of us dyno with the boats exhaust. I for one will sometimes. I use headers with a primary of 2 1/8" with 8 O2 sensors. So installing 8 O2 sensors in a set of marine headers isn't going to happen. You can pretty much tell; with injector fuel flow and O2 # data from dyno to boat if the headers are getting the scavenging done. If the O2 readings go rich, the engine is being restricted, if it leans out; well you get the picture.
Yes, exhaust flow is important on a NA and a forced induction.

On Time

I DID have one like that once...

bcfountain

I would like to have a set of headers on one of my boats,,,,,,,but after all the bad stuff I hear about the headers leaking ,I will pass.my 10meter has ssmarine manafolds and dry risers.i will say this about ssmarine products.the last,and last,,,,and last some more.my first go fast boat was a 22pachanga.i put ssmarine manafolds and risers.this was in 1998.i sold the boat years ago.two different people owned the boat after I sold it.the new third owner I know.those manafolds and risers are the same ones I bought in 98.the boat has had blowers motors,big inch motors and a host of other motor combanations.my point.stainless marine make good stuff that last.

Boater8987

How about having to pull heads or engines to gain access to install fixture to re drill bolt pattern on a twin side by side or even a tight single? Or is it possible to gain enough room to install fixture and re drill? Most people would have to pay a shop to do that. I had SM on a staggered 33 Powerplay and the forward motor broke two sets of flanges off manifolds at tail pipe and manifold flange, where clamp goes, in under a 100 hrs. The set up was custom built by Stainless. So they are not unbreakable either. Yes it did have long tail pipes and were well supported. Powerplays are well built boats but I guess it was still flexing because of length. Stainless did warranty the first pair. I still think they are very good manifolds and customer service was very good. But you will still have to add in the extra install expense for 525-700 SCI applications and they are not indestructible. As we all know salt loves aluminum too. I now have 600SCI's, in my Spectre, with good ole proven CMI etops adapted by Teague Custom Marine to fit header flange bolt pattern and bungs installed to bolt antifreeze reservoir to. I sold the sweepers off the 600SCI motors and purchased etops and plugged right in to my existing tail pipes from my 575 SCI's. Old etops were 11+ yrs old and sold with motors. Never had an issue.