Head is off. Two plugs clean, four sooty, water evidence?

[deerhuntre]

1975 Mercruiser 250ci 165 hp.

The two cylinders closet to the stern have clean spark plugs and a pretty clean valve. The other four cylinders are black like the picture with pretty sooty plugs. The cylinder at the other end by the thermostat was much less sooty. Are the clean ones being steamed cleaned from water? What is the likely cause?



The end two are like this:

The other four are like this:

And here's two next to each other for comparison:

 

[Bt Doctur]

Re: Head is off. Two plugs clean, four sooty, water evidence?

Thinking a leaky riser dumping water into #4 cylinder

 

[deerhuntre]

Re: Head is off. Two plugs clean, four sooty, water evidence?

So what do I do if its a leaky riser? Is that something to replace or just a gasket? I don't see any cracks in the exhaust manifold or the riser, but I'll look more closely with a really bright light again.

 

[Bondo]

Re: Head is off. Two plugs clean, four sooty, water evidence?

I don't see any cracks in the exhaust manifold or the riser,

Ayuh,... It's usually the gasket surfaces, between/ on of, the manifold, 'n riser...

Post a picture of each of 'em...

 

[deerhuntre]

Re: Head is off. Two plugs clean, four sooty, water evidence?

Exhaust manifold:

Riser:

Head and manifold gaskets:

Manifold gasket:

 

[Bondo]

Re: Head is off. Two plugs clean, four sooty, water evidence?

Ayuh,... The Manifold don't look too bad, but I'd probably pull the studs, 'n flatten/ clean it with a few strokes of a flat file...
The riser is lookin' pretty Rough,...
It definetly needs flattening with a file, or replacing...