I'm putting a GM ls motor in my pontoon. (http://www.offshoreonly.com/forums/r...oon-build.html)

Like everything I do I prefer to make it or build it myself. With not alot of options out there for LS exhaust I designed up some that I belive will work. Before I start making chips and sparks I thought I would see what you guys thought. Attached are some screen shots of the exhaust.

I havent complete made up my mind on what kinda of Material I want/should use. This boat is a fresh water only boat that does not sit in the water for long periods of time.

The primary leaving the exhaust ports right now are SCH 10 tubing 1.9"ODx1.625"ID they go into 3" tubing. The water jacket is 4" tubing.

Thoughts?

These will also have 02 sensor bungs in them so I can run a closed loop fuel system.

Thanks
Mike

It'll work,not the most efficient design,,but easier to build.

Uhm, there is everything from basic manifolds to full on marine headers and everything in between avail for ls motors these days. I get you want to make your own stuff, but if your exhaust fails, cracks etc it wont be pretty or cheap

I agree put its got to be better then the old cast log style manifolds. What modifcations would you make? Any worry about the 90 degree bends coming off the heads not being water cooled?

You are right from a 800 to 3000 dollars. Most the material we have at work except the 4" 90 I would have to purchase that so my price wouldnt be all that bad.

As far as failing goes not to worried about that anything can fail and I understand what will happen. If this was a offshore boat it would be different but this boat stay mostly on lakes and sometimes see rivers.

I'd be water cooling them,,it will be glowing red on a hard run.they won't burn thru w/ the material you have,,I guess if you had to,get them coated inside and out.

I'd also try to get better angles to the out pipe,less 90° bends.Try to smooth them out a little.

I would be concerned about the unjacketed part coming of the head, as it will be extremely hot. Both for safety as well as the temperature difference could cause cracking. The common dump wouldn't be any better than log style manifolds, if you could separate the runners it would be better.

Also one fatal flaw...these are water jacketed, yet no provision to introduce water????

I'm wondering if I even need that 90" coming up. The top of the 90 is at the top of my intake manifold for reference. I understand that you want to try and get them as high as you can out of the water so water wont push back which would be very bad.

Would coming straight out the back with a slight turn down work? Only issue I can see is water pushing back up.

Thanks again for your help, I know just enought about boats to dream up these things. lol

The water would enter at the bottom of the 4" log front and back and exit thru the yellow ring. Never drew the inlet in as those are just 1/2 npt bungs that would get weld in.

I havent ruled out just buying manifolds as it would be easier but I dont alawys do the easiet thing.