Head - Manifold Mating surface

Anyone have any suggestions on what i should do with the corrossion on head mating surface? Do i need to have it machined before i install a new manifold? This is on a 2007 Mercruiser 3.0L

Re: Head - Manifold Mating surface

From what I can see in the pic the surface is rusted to the point of material being gone on more than 50% of the thickness in mating surfaces in some areae. If thats true- I think the answer is yes -- on getting it machined. Perhaps an engine shop could verify that for you.

Re: Head - Manifold Mating surface

Some of the exaust mani gasket have bigger ports than the heads but do match the mani especially on the LX'S I know mine are but compare a new gasket to the head and see f the surfaces match where the old matting surface is . But for being only 5 yrs old thats pretty corroded.

Re: Head - Manifold Mating surface

I would as a last resort double up the gaskets before i would resort to machining.

Re: Head - Manifold Mating surface

The exhaust and water can't mix at this point.I would lightly sand everything and re install with a new gasket

Re: Head - Manifold Mating surface

Ok. Thanks everyone. I will lightly sand and reinstall with a new gasket and see how things go. Ran like me before I took it off. I'm just frustrated with this corrosion. I always flush and flush with salt away, never leave the boat in the water (davits and foam block cradle), and I spray the entire power package with corrosion block spray every other month. Even though I also pull the plug after use and have the bow high there is always about a half gal or so of water that sits in the bildge at the back from the boat wash down water. Maybe I need to shop vac all that out everytime too??
This is the first I've owned my own boat in salt water. I've always live on a lake. But that's not an option here in the Florida Keys!

Re: Head - Manifold Mating surface

The corrosion is not good. It is indicative of a problem. like raw water intrusion through the exhaust.

Part of the issue is the "cold" sea water contacting the hot exhaust valve, making them brittle and prone to breakage.

A safe option would be to do a valve job and swap out the valves. At that time the head should be inspected for possible replacement.

The exhaust should also be inspected for possible replacement.

Re: Head - Manifold Mating surface

The valve is clean. The corrosion is limited only to the mating surface on the head due to the riser/manifold gasket failing and leaking down for some time....you would still do a valve job? Or replace the head?

wingless said:

The corrosion is not good. It is indicative of a problem. like raw water intrusion through the exhaust.

Part of the issue is the "cold" sea water contacting the hot exhaust valve, making them brittle and prone to breakage.

A safe option would be to do a valve job and swap out the valves. At that time the head should be inspected for possible replacement.

The exhaust should also be inspected for possible replacement.

Click to expand...

Re: Head - Manifold Mating surface

I'd machine the head. I'd also be shopping for a closed cooling system to keep from needing to replace the head later.

Re: Head - Manifold Mating surface

As this is a saltwater operated engine I would be asking for more troubles putting a closed cooling system on it unless it was a new motor...

wingless said:

The corrosion is not good. It is indicative of a problem. like raw water intrusion through the exhaust.

Part of the issue is the "cold" sea water contacting the hot exhaust valve, making them brittle and prone to breakage.

A safe option would be to do a valve job and swap out the valves. At that time the head should be inspected for possible replacement.

The exhaust should also be inspected for possible replacement.

Click to expand...

NHGuy said:

I'd machine the head. I'd also be shopping for a closed cooling system to keep from needing to replace the head later.

Click to expand...

Re: Head - Manifold Mating surface

OK so later when it corrodes through get closed cooling for the next motor, I guess. Too bad that corrosion, stinks to have a 5 YO motor looking like that.

Re: Head - Manifold Mating surface

wingless said:

The corrosion is not good. It is indicative of a problem. like raw water intrusion through the exhaust.

Part of the issue is the "cold" sea water contacting the hot exhaust valve, making them brittle and prone to breakage.

A safe option would be to do a valve job and swap out the valves. At that time the head should be inspected for possible replacement.

The exhaust should also be inspected for possible replacement.

Click to expand...

Jiminthekeys said:

The valve is clean. The corrosion is limited only to the mating surface on the head due to the riser/manifold gasket failing and leaking down for some time....you would still do a valve job? Or replace the head?

Click to expand...

Here is your image blown-up and enhanced.

It looks like the corrosion extends to the interior of the head.

The engine would not have this corrosion under normal operation, unless something like exhaust raw water intrusion caused this damage.

The outcome is Boolean, either the valves are damaged and will fail, or they are fine and won't fail. If the valve fails then hardened steel fragments will bounce around the combustion chamber of a moving engine. That won't be a good day...

There is nothing good shown on the image. The corrosion is inside the exhaust port.

If it were me I would disassemble the engine and bring the heads to an expert. They can either be salvaged or not, also Boolean.

Chances are likely that the exhaust problem is not just a failed gasket, but intead worn-out parts, like the manifold, riser and knuckle. Those parts wear-out, permitting this damage. Those parts require sufficient SOLID wall thickness at the gasket surface, between the raw water and the exhaust passages.