Exhaust Manifold Installation Help Needed
 

I'm getting ready to install replacement exhasut manifolds. Project is on a budget becuase of other issues si I'm using GLM manifolds with 3" riser blocks and Mercruiser stainless steel elbows. Closed cooling system.

So the questions--

1> which Manifold gasket that should be used between manifold and head?

2> surfaces on manifolds, riser blocks and risers are all painted--what surface prep is required on these surfaces before mating?

3> gasket configuration to be used between manifold and 3" riser blocks and sealant used there--if any. (these will aloow closed cooling water to circulate from the manifold thru the extension blocks

4> gasket configuration to be used between riser blocks and risers and sealant if any (these will have solid stainless plate beacuse raw water exits cooling system hre to go overbaord with exhaust.

5> can stainless steel studs/nolts be used to connect the risers/blcoks to the top of the manifolds?

I know this seems like a lot of nits but we got into a big long (expensive) discussion last time around about sealnts and gaskets and got some really conflicting advice from Mercruiser, Barr, MarinePower to name a few.

What we did has held for 4 years but things have changed also. Seems like there was a bulleting back then from Mercruiser about the best gasket sealer to use--in my senile state I can't remeber the whole circle-jerk we went thru.

Thanks for any thoughts and advice. I want to get all the materials together and rehears this a few times so I only have to do it 3 or 4 times to get it right.

Re: Exhaust Manifold Installation Help Needed
 

Manifold/riser installation tips:

Paint all exterior surfaces (unless you get the OEM ceramic coated manifiolds).

Don't use the paper gaskets that come with aftermarket Manifolds, use OEM Mercruiser gaskets. Much easier to work with (remove).

All gasket surfaces need to be flat. If the paint is flat, you don't need to remove it. If you have to scrape the paint off to be flat, scrape it.

NO sealer on gaskets, liquid thread sealant (not teflon tape) on anything that threads into the manifold (plugs and studs or bolts).

Chase all threaded holes with tap before assembly. Use new grade 5 (not stainless) or better bolts/studs or clean threads throughly.

When using the 3" riser extensions, don't mount the risers with long bolts. Use grade 5 or better studs and nuts. With no riser extensions, use grade 5 or better bolts.

Thread two 3/8" studs with slot cut in the end into the head to hang gasket and manifold while installing mounting bolts. Then remove studs with screwdriver (using slot cut in the end) and install last two mounting bolts.

Dave

Re: Exhaust Manifold Installation Help Needed
 

Check the inside of the GLM manifolds. I'm planning on using them when I replace mine in the spring, but I've heard a few people complain about excessive casting flash inside the manifolds. You might want to clean that up before installing. I know I'll be checking mine out. I also use a liquid gasket/thread sealer on the bolt threads only (not the gaskets), and I've never had any trouble getting them out at a later date. The stuff I use is OMC branded, but I know Mercruiser makes it too.

Re: Exhaust Manifold Installation Help Needed
 

I've got the 4 manifolds but only taken one out of the box. The insides are extremely well finished--seems like some sort of coating inside. In fact the exterior finish is well done also--especially as compared to the OSCO's that are on engines now. These also seem lighter than the OSCO's/

I'll inspect the rest of them in the next day or two.

The stainless steel elbows and the riser extensions should be here tomorrow. Next step will be the plumbing fittings, anodes and the drain plugs.

THanks for the heads up on inspection.

Re: Exhaust Manifold Installation Help Needed
 

Dave N--FYI--had to send the B&G Engine Sys back to them under warranty. Turned out the thing was defective. They have now sent it to England to further test and repair. Hope I get to see it in boat before the season is over.

Re: Exhaust Manifold Installation Help Needed
 

I'm glad to hear the manifold looks good.
They say those manifolds are hot dip galvanized, then the outside is powder coated. I also hear they're lighter because of the lost foam casting process (more accurate).
What are those stainless elbows costing you?
When I replace the manifolds, I'd like to run something better than the stock risers.

Re: Exhaust Manifold Installation Help Needed
 

Dave's right on the money for your installation as far as I'm concerned. The studs with a slot are a great trick and make the job soooooo much easier. Without them, you'll be cussing. Sometimes you run in to a little clearance issue with the bolts, but hopefully that won't be a problem for you.

Good luck.

Re: Exhaust Manifold Installation Help Needed
 

Dave, Why not use stainless bolts? Curious. I am talking about securing the exhaust manifold to the head.

Re: Exhaust Manifold Installation Help Needed
 

The manifold I unpacked and examined does seem lighter than I expected.

I got the risers from Don's Marine Salvage in Clearwater/St Pete. They are an institution and have a website think is www.donsmarinesalvage.com

Re: Exhaust Manifold Installation Help Needed
 

Dave, Why not use stainless? Curious why not in a marine environment. We are talking about the header attaching to the head, right?