Manifold Erosion

[mmeinhold]

I have severe rusting and erosion at the exhaust end of the manifiold, including the exhaust flange and the water exit flange. As you can see the tapped hole for the exhaust flange is almost gone.

Early Model 1965 in Alberg 30.
Had this manifold off 3 years ago, acid flushed and painted. Engine is SW (upper Chesapeake) cooled.

I have never observed any leakage around the water exit, or that these surfaces were wet.

I have a replacement manifold. It's a new model so required some replumbing.

What is likely causing this ???? Any ideas or wisdom would be appreciated.

Mike - Rinn Duin, Alberg 30 #272

[Dave Neptune]

Tt's shot

Hi Mike, first welcome the the MMI Afourian Forum.
That looks as if the fitting had been leaking for quite a while. It does not need to look wet to pass enouigh salty water to keep rusting away.
I suggest when replacing the manifold and gaskets you use a permatex NON-Silicone type. Use the Aviation Grade preferred by me or Permatex #2, either will work fine.

Dave Neptune

[JOHN COOKSON]

By the looks of it my uneducated guess is there has been some dissimilar metal electrolysis going on also.

TRUE GRIT

[romantic comedy]

I totally agree with Dave.

[joe_db]

Run the engine at night and shine a bright flashlight all around. On my old engine I found several pinhole leaks that were misting the engine with salt water. Also note a leaky manifold stud will let water in what would normally be the dry section.

[hanleyclifford]

On your new manifold make sure to use studs, not capscrews to secure the flange. Use Permatex #2 to seal the threads in the casting.

[mmeinhold]

Manifold Erosion

Thanks all - I pulled off the exhaust flange (Moyer's version with a tap for back pressure measurement) , cleaned it up and painted with hi-temp paint. I will dress the mating surfaces and follow the Permatex #2 advice.
The water exit on the new manifold is a hole tapped for threaded pipe.

I will check it for water spray carefully when I reinstall (soon!)

Mike

[sastanley]

Mike, I am right there with you. I discovered my aft manifold stud was probably leaking for years. I think the manifold & block are OK...they are not as corroded as yours..So...today, in Solomons, MD the temp was warm enough to finally get the JB Weld to cure to hopefully secure my nice fresh Moyer oversized stud.

At any rate...if I had caught the leaking 4 years ago when I initially owned the boat, I might have caught it earlier and fixed it without the totally disintegrated stud, which I found this winter.

We'll do whatever we can to help you out.

Oh...and welcome..sorta, since you are probably a lurker with your 2009 sign up date!

[Dave Neptune]

A second thought

Mike, from the looks of the manifold water exit I'm "guessing" that the hose was clamped to the threaded piece sticking out~?~a big No No as it will not seal. I have seen this attempted many times and they always seep a bit. If not make sure of your "mating" surfaces and check for seepage.

Dave Neptune

[mmeinhold]

No, that nipple was threaded into a T with the thermostat. I am careful to convert hose barbs where hoses are attached.

[Al Schober]

Another thought. There seems to be a white line in the photo suggesting a crack in the manifold. Perhaps winter freeze damage?

[hanleyclifford]

By the looks of it my uneducated guess is there has been some dissimilar metal electrolysis going on also.

TRUE GRIT

For which reason it is best to come out of the casting with a steel or iron fitting before going over to bronze, especially where salt water is involved.

[mmeinhold]

Update on Manifold erosion

After reviewing my hot section - brass, I realized that my water inlet was about 1/2 inch higher than Moyer's recccomended 4 " minimum from the top of the water inlet to the highest point on the bottom inside of the exhaust pipe. My theory is that i was spillling water back into the manifold with some regularity. This fits with the white exhaust I have been seeing. I put a 4" nipple on and hope that does it. Should be starting it tonight after getting the engine remounted last week.

Mike

[romantic comedy]

Mike, if I understand. You are saying that you are a 1/2 higher then the minimum?
If that is the case, then you are more then the minimum....

[edwardc]

After reviewing my hot section - brass, I realized that my water inlet was about 1/2 inch higher than Moyer's recccomended 4 " minimum from the top of the water inlet to the highest point on the bottom inside of the exhaust pipe. My theory is that i was spillling water back into the manifold with some regularity. This fits with the white exhaust I have been seeing. I put a 4" nipple on and hope that does it. Should be starting it tonight after getting the engine remounted last week.

Mike

Mike,

I don't know if that's going to turn out to be the source of the problem.

Refer back to your original post with four pictures. The one that shows the manifold's exhaust flange mounting area clearly shows that the inside lip of the opening is un-erroded, while the outside lower bolt-hole area is badly eroded, but from the outside. To me, this says that water was dripping down around the outside of the flange, probably leaking from the pipe nipple area on the manifold's cooling water outlet. The pattern of rust on the outside of the manifold, all the way up to the base of the pipe nipple, appears consistent with this idea, even though you never observed wetness at this area. It would only take a little, and it would boil off quite quickly. But over time, the damage would add up.

The other possiblity is a weeping crack in the manifold's water jacket in this area. Have you pressure tested it?