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joseph m. hahnl
05-04-2014, 07:25 AM
I finally put the aluminum exhaust manifold on. Found anti freeze in the exhaust ports both sides. Some one smiled down at me "if you know what I mean" as all the valves were closed:worthy:. I thinking the riser gasket were leaking. I put in a SS block off plate and double gasket, But it means the gasket was leaking from the underside or the manifold's water jackets were leaching. Odd that it's on both sides. I'm a little worried that there might be porosity in the aluminum heads and it's passing through:boggled:

Carl C
05-04-2014, 10:29 AM
Sounds like a bad heat exchanger. It doesn't take much to damage the inner tubes.

duckhunter
05-04-2014, 10:40 AM
Kinda scary! Sounds like you caught it in time though.

Not sure of your exact setup, but I stuck brand new GLM aluminum manifolds & risers on the boat a couple of years ago. Before I installed them I checked all of the mating surfaces for flatness and a couple of them were pretty far out, and all of them needed attention. I used a sharpie, a steel ruler, and a good file to get them dead flat. Took about an hour. The aluminum really expands & contracts with heat cycles, dramatically more so than cast iron, so I wanted to make sure they were good and flat to begin with.

Also, the hardware loosened up appreciably and needed to be retorqued to spec after the initial run on the hose.

I know the current exhaust TSB from Mercruiser says to install the graphite riser gaskets dry, but I use a tiny coat of Permatex aviation gasket sealant on all of the mating surfaces & hardware and it makes me feel better.

Curious to hear what you find. Good luck!

Ghost
05-04-2014, 11:10 AM
If there's ANY chance that fluid got into the cylinders, not much work to pull all the spark plugs and turn it over to blow them out.

joseph m. hahnl
05-05-2014, 09:29 PM
Sounds like a bad heat exchanger. It doesn't take much to damage the inner tubes.
Hmm:confused: So your saying it could back feed through cold side. I'll pull the riser hose and see if anti freeze is in it, but I don't recall any coming out of the hose when I put the new manifolds on. I'm battling a slight tac pulse or rather surging and I had hoped the new riser gaskets would alleviate it. It may be an internal vacuum leak or a short some where. The hunt begins:rolleyes: