Exhaust manifolds

[bobv]

I just installed new manifolds risers and elbows on a 1980 with chrysler engines I pulled the brass plugs fron the bottom of the logs.
All were dry except the two near the risers. These had water in them #8 and #7. Is this normal?
Thanks
Bob

[bobv]

The water in the exhaust where the brass plugs is not normal. I installed the risers ond with silicone sealant. I looked up the recomendations from osco they say do not use silicone or you can have leaks. I removed the sealant as well as the paint installed new gaskets dry and have no issues.
My second engine was installed with silicone but had no issues.I decided to change the gaskets and clean the parts as recomended and installed the new gaskets dry. If you see water in the brass plugs there is an issue with your exhaust.
Bob

[EWRice]

This is a common issue I see with the log manifolds. The ends of the manifolds, block off plates, and risers/outlets seem to rust enough so that they won't seal good. I have made it a habit to never install used/used or new/used components together without refacing the old parts. I just sent a group of manifolds to have their gasket surfaces faced yesterday. The risers and block off plates I can handle in my mill.

[bobv]

I had all new parts and put silicone to seal them , a mistake on my part, you should install as per manufacture's instructions.
These parts have milled surfaces that you cannot see with the factory paint on. Once the paint is removed as per instructions you can see the milled grooves. This is why the gaskets work without sealants. I will not use silicone on these gaskets again!

Bob

[EWRice]

I have also found that there are different grades of gaskets. I try to use the ones from Marysville Marine. They are a thicker, more dense material and I have had better luck with those gaskets. Either barr or osco supplies similar gaskets. Some places supply a thin black gasket that does not hold up well.

[Tranquilo]

After reading this thread, I got my riser kit for the exhaust manifolds. The boat had the old setup without risers and a wave in the a$$ flooded out my 8.

So I bought a whole new manifold, riser, elbow for the starboard and since the port side is only 4 months old, I bought a riser for that side as well.

I pulled the elbow from the manifold (the 4 month side) and noticed rust specks all inside the hot exhaust side. I did use the silicone and see where it may have contributed. I scraped the old gasket and silicone off and sanded it down to the metal. I used new gaskets and installed the riser.

Do you think this was caused by a gasket failure or the fact that the exhaust has been full of water all the way up to the elbow while sitting for so long?

I am ordering new end plates and gaskets so those are new and have fresh gaskets too.

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[Fastjeff]

This subject is near and dear to my anger bone! I had water issues for years on mine until I learned to silicone both sides of the gaskets when installing the risers.

The problem is a combination of gasket surface warpage over time (and heat), plus improper tightening of those 4 bolts. The weight of the riser hanging on the manifolds tends to make the top bolts do "less work" (so to speak) than the lower ones. So, when installing, I've learned to snug the top ones first, then the bottoms, then tighten the top ones, then the bottoms. (This is opposed to the usually correct method of cross tightening.)

Finally, I know OSCO and Barr literature says to not use a sealant, but they are talking about NEW parts that aren't warped. On other marine websites, this subject has been heavily debated with the Siicone appliers winning handily.

Jeff

PS: In the above photo, note how narrow are the gasket surfaces keeping the water out of the exhaust--and see how many places it can get in there (especially at the bottom).

[Tranquilo]

I ordered an "end plate gasket kit" with two gaskets in it. One looks like the rest but the other is a ring that is the size of the exhaust chamber. Does anyone have experience with this?

http://www.boatpartheadquarters.com/Chr ... 8-2941.htm

Its listed in the IPB but doesn't specify the usage
http://www.iboats.com/Chrysler-Inboard- ... _id.272946

Also, I was able to turn the bolts on my manifold end plate about 1/3 of a turn so that made me comfortable enough to start it to set my timing.

After installing risers (they just had manifolds & elbows) the manifolds run way hotter (175 degrees on each side) the risers are around 185. I'm a bit alarmed because the hoses were so hot, I'm worried about them failing. I did expect the riser setup to run hotter because the whole flow will be slower at idle because of the added area it needs to fill. The elbows are really cool though - 115.

Am I just new to this riser thing or should I be concerned? I'm postponing my test run until tomorrow so I don't break anything.