Corroded exhaust flanges stainless marine manifold

[Ralph Savarese]

Yesterday while doing a routine spark plug change I removed my manifolds for access and discovered piles of corrosion in the middle exhaust ports on both sides. So investigated up higher by removing the risers and discovered that the exhaust flanges on the inside were significantly corroded away. It is not salt I tasted it! It appears to be a galvanic reaction between the riser and the manifold caused by the exhaust. If I didn't remove the manifolds I would have never discovered this the engine as been running perfect these manifolds are 4 1/2 years old you guys have any thoughts? I already contacted stainless marine and sent them the attached pictures waiting for a response. Other than that these manifolds have been great.

[gcarter]

I would have thought the gasket would have been an adequate isolator.
What did the gasket look like?

[Ralph Savarese]

The gasket just crumbled with all the corrosion when I separated the riser

[gcarter]

OK, I'm just guessing.....have you checked all the engine's and gimbal bonding grounds?
Do you ever keep it in the water?

[Ralph Savarese]

The boat is kept on the trailer in my garage and is flushed after each use with salt away. The only thing I could see is that maybe a gasket failure caused connection between the riser and the manifolds there for causing a galvanic reaction. The gaskets were basically dust. I am hoping stainless marine will do something for me there is a 5 year warranty waiting for a response spoke to them today.

[Ralph Savarese]

Jerry at stainless marine says it is a slight reversion issue. I find that hard to believe I tasted it! It is not salt. The gaskets were dust! I belive the gaskets cracked causing a galvanic reaction. reversion would be more in the back cylinder ports not in the middle ports alone this fell straight down. Very wierd

[gcarter]

That's an interesting response from them....
Thinking of Gil (and Hardin follow on) manifolds, they include a conical "Turbulator" in the joint
that theoretically keeps any reversion water in air suspension.
It's #24 in the picture:



I have to assume it works as I have a nearly 20 year old set of manifolds in my shop
w/o any signs of corrosion.

[Pat McPherson]

Do you have the short risers?
What cam are you running.
What does she idle at?
When I've had leaky risers or reversion issues, I would see signs in the exhaust ports too.

[Morgan's Cloud]

Jerry at stainless marine says it is a slight reversion issue. I find that hard to believe I tasted it! It is not salt. The gaskets were dust! I belive the gaskets cracked causing a galvanic reaction. reversion would be more in the back cylinder ports not in the middle ports alone this fell straight down. Very wierd

To be honest , when I saw the white speckling on the carbon covered exhaust passages that was the first thing I thought of too .

It would seem that not all problems manifest themselves in the identical way from one case to the next. Life would be just too simple then !
The good thing is you caught it in time and can rectify it before it does any greater damage .

[Ghost]

Jerry at stainless marine says it is a slight reversion issue. I find that hard to believe I tasted it! It is not salt. The gaskets were dust! I belive the gaskets cracked causing a galvanic reaction. reversion would be more in the back cylinder ports not in the middle ports alone this fell straight down. Very wierd

One observation with no conclusions: i think if the gaskets crack and don't seal, it may cause water to get sucked back toward the joint.

[JParanee]

One observation with no conclusions: i think if the gaskets crack and don't seal, it may cause water to get sucked back toward the joint.

all I can say is that salt water sucks

[Pat McPherson]

One observation with no conclusions: i think if the gaskets crack and don't seal, it may cause water to get sucked back toward the joint.

One good thing about the stainless marine system is that the riser manifold join is not wet; the gasket only seals the exhaust gas.
To have water inside the manifold, it could really only be a leak in the riser or reversion. I don't think you'd find both risers would leak after 4-1/2 years.
Another remote possibility would be water splashing back up through the exhaust while the boat is anchored. Do you have flappers?

If you could provide this info, maybe we can provide a little more insight.
Are you running the short risers?
Do you have the spec of your cam?
What does the engine idle at?

[Ghost]

One good thing about the stainless marine system is that the riser manifold join is not wet; the gasket only seals the exhaust gas.
To have water inside the manifold, it could really only be a leak in the riser or reversion. I don't think you'd find both risers would leak after 4-1/2 years.
Another remote possibility would be water splashing back up through the exhaust while the boat is anchored. Do you have flappers?

If you could provide this info, maybe we can provide a little more insight.
Are you running the short risers?
Do you have the spec of your cam?
What does the engine idle at?

Yep, exactly, I'm speaking not of a situation where water is leaking out of compromised manifold or riser jackets, I'm speaking of water from the proper mixing location aft being sucked forward toward the motor (reversion). I've seen it with my own eyes with an old, bad gasket that was a mess generally, and missing about a 1/4" section maybe.

My tails are VERY long. Longer than almost any I've seen. And they turn a 90 degree out/30-ish degree downturn when they reach the transom, all before the water is mixed in. Stock 496 Mag HO, 425 HP. Weird sh1t happens in exhaust at 800 RPM with a little cam overlap. Shut it down immediately. Pulled the plugs and turned it over to make sure the water was out. Pressure tested the manifolds and risers both--both perfect. Talked to Jerry. He confirmed that crazy stuff can happen if the system isn't sealed. Replaced the gaskets.

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[MOP]

I am with Steve's assessment! Do you have the Turbulators in your setup? If not I would get a set.

Phil

[Fishermanjm]

Turbulators??? Get new gaskets from SM??? I think I'm taking mine apart
as part of my get-em-ready maintance. How about the thick manifold gaskets
that take up the unevenness head mating surface??? Where can I get them???