3.0 mercruiser

[realslimshady]

Any advice welcome...
Have just pulled the head on my 1990 vintage 3.0 Mercruiser, suspicious that I had problems...well founded suspicions, it seems.
Cylinders 2,3 and 4 are all covered in surface corrosion,as are the exhaust valve ports and valve stems etc. I seem to remember reading somewhere that the exhaust manifold can become porous and let cooling water in-does that seem likely? At first I thought cylinder head gasket but it looks ok and the state of the ports seems to rule it out. Interested to hear anyones views!

 

[spannerman]

The exhaust bend on this motor is very prone to corrosion with age and they can leak seawater at the gasket between manifold and bend, giving the problems you have, so I would check that before condemning the manifold.
The fact that its the 3 cylinders nearest the exhaust bend indicates the water came from that direction.

 

[Elessar]

You might find this parts catalogue useful.

 

[realslimshady]

Spannerman-thanks. Think you are spot on-joint between the manifold and the exhaust bend was a right state-will get that leak-free and see how we go. Manifold shows no sign of leaks berween the jacket and the ports, at least when cold.

 

[overdrawn]

Hi I had similar problems myself a couple of years ago,the manifold on port engine had failed stb ok,at that age I believe it would be wise to change the manifold and riser anyway as it is only a matter of time,pattern parts from keypart some times need a bit of fettling around the bolt holes but are cheap and seem to last ok. A small price to pay for peace of mind and reliability esp if you do longish trips