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Bozboat

What's in your Exhaust Manifold

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Bozboat

ok, a month or go or so, in some other thread, there was a difference of opinion on whether the bottom of the exhaust manifold (at the point where the exhaust leaves the head into the manifold) was water cooled? This is the area on the bottom of the manifold where the paint seems to cook off.

I cut open my exhaust manifold that I retired last winter. It has been outside for awhile, so it looks rough on the outside. After cutting it open, I believe that there is no water flow under the bottom of the exhaust manifold, where the paint burns off first. The water flow appears to be confined to the triangle section and does not dip down below the exhaust ports. I need a new grinding wheel to finish this off, but here is the first set of pictures.

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IMG_3497_zps5c2ec868.jpg

IMG_3498_zpsdf63e693.jpg

IMG_3499_zpsf62d8031.jpg

RL]

Edited by Bozboat

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Asmodeus2112

But does it blend?

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Bozboat

But does it blend?

Oh, I neeed a BLENDTEC

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Sixball

Do you winterize? If so do you just drain water or do you use antifreeze?

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Bozboat

Do you winterize? If so do you just drain water or do you use antifreeze?

I drain and leave it. I bought the boat with 450 plus hours on it and some of the funk on the inside of things has me wondering if all this is normal for the hours.

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shawndoggy

what *is* the "funk"? Rust or dirt?

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Oberon

The manifolds are iron if I'm not mistaken. I think the idea is to build them thick enough that the engine will be functionally obsolete before the corrosion takes its toll. Once the corrosion starts it acts as a protective barrier to the rest of the structural metal. I don't see an issue with the rust.

One could probably make a fancy multi piece milled stainless/aluminum/titanium (take your pick) water jacket but it would cost a fortune and the only real benefit would be weight savings, which isn't as useful on a recreational boat as it would be on, say, an airplane.

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Bozboat

The manifolds are iron if I'm not mistaken. I think the idea is to build them thick enough that the engine will be functionally obsolete before the corrosion takes its toll. Once the corrosion starts it acts as a protective barrier to the rest of the structural metal. I don't see an issue with the rust.

One could probably make a fancy multi piece milled stainless/aluminum/titanium (take your pick) water jacket but it would cost a fortune and the only real benefit would be weight savings, which isn't as useful on a recreational boat as it would be on, say, an airplane.

I think you are correct that the manifolds are cast iron. There is a level of mud like rust in them, but they were fully functional when I pulled them off. I just hope that the inside of the block doesn't look like the inside of the manifolds, but that's just me fretting about stuff that I can't do anything about. Boat runs great, lakes are dry, kids are in school, so nothing to worry about this year.

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Oberon

I'm sure the inside of the block looks like the inside of the manifold. Once the rust covers the iron it slows down the decaying and provides a level of protection. In 100 years or so it might be a problem. I wouldn't worry about it. :D

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Sixball

This is why I chose to go with antifreeze. (JMHO)

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nuttyskier2002

Sixball, unless you are draining the block and backfilling w/anti-freeze after each use........I'll bet your block doesn't look much better than his inside. Anti-freeze does nothing to correct any corrosion that has already taken place. And Oberon is correct in saying that the surface corrosion provides a layer of protection for the bare metal beneath it. It's the same concept as anodized aluminum.

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shawndoggy

won't the exhaust manifolds gravity drain after you shut down anyway? Even if you did run antifreeze after every use, it wouldn't stay there would it?

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martinarcher

Nope, they sit full unless you drain them.

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shawndoggy

how does the water get out of the manifold to the exhaust?

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Bozboat

how does the water get out of the manifold to the exhaust?

Water goes in the side at the elbow, fills the manifold exits the manifold on four sides of the exhaust

9D86EAD7-960A-4571-87DF-D7D205BB9CF2-263

then goes out the top where the four water channels meet the four channels in the riser

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from the manifold the exhaust goes out the middle, the water around the edges into the riser

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then at the end of the riser, the exhaust and the water mix right before the exhaust hose starts

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Edited by Bozboat

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Bozboat

I am guessing that if the water and exhaust mix in the manifold somewhat that's how you backfill the heads with lake water

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nuttyskier2002

The "mixing" is actually done in the elbow not far from where the hard wall rubber exhaust hose connects. They are designed to "minimize" the risk of water ingestion into the exhaust and getting into the cylinders. Still it is possible for this to happen under the "right" or should I say wrong conditions. The manifolds should be removed pressure checked and gaskets replaced about every 6 to 8 years.

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nuttyskier2002

And yes.........you need to drain the manifolds to get the water out of them. The block drains will not do this. The LCR and Monsoon engines have a water hose from one manifold to the other that when disconnected will drain both. Older Mercruiser engines have individual valves at the bottom of the manifold for draining.

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Sixball

Sixball, unless you are draining the block and backfilling w/anti-freeze after each use........I'll bet your block doesn't look much better than his inside. Anti-freeze does nothing to correct any corrosion that has already taken place. And Oberon is correct in saying that the surface corrosion provides a layer of protection for the bare metal beneath it. It's the same concept as anodized aluminum.

The only time I drain is just before I put the antifreeze in, other then that the boat is full of water. If it has water you do not have oxygen rich damp air. I also am still on the original impeller. It will be replaced before next spring. Another of my ski partners with a CC196 is on an impeller 8 years old. He also uses antifreeze. I do not get rust or junk when I drain the block. so I think it is keeping things clean and rubber in good shape. I winterize other boats that do drain and get significant rust when draining them! Oh I have done this with all my boats from new to sale.

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Oberon

The "O" in H2O is "oxygen". You are confusing "air" and " oxygen". Dry air also contains oxygen but it is the electrolytes in water which starts the chemical reaction. Interestingly, humid air will rust iron but distilled water (no electrolytes) will not. Lake water is not distilled so the iron parts of your engine are rusting.

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Sixball

The "O" in H2O is "oxygen". You are confusing "air" and " oxygen". Dry air also contains oxygen but it is the electrolytes in water which starts the chemical reaction. Interestingly, humid air will rust iron but distilled water (no electrolytes) will not. Lake water is not distilled so the iron parts of your engine are rusting.

True but I think you will find if its in water the speed it does is much slower.

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Oberon

Not true. The minerals in the water act as a literal electrolyte bath which assures a continuous chemical reaction. In the air, the reaction can only occur when an electrolyte occasionally bounces into it.

If you don't believe me find two pieces of iron. Place one in a bucket of lake water and another on the ground next to the bucket. Report back which rusts sooner.

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