Merc 7.4 1997 steam out of valve cover

[AMR]

Hi guys! This boat (Sea ray 240) runs great, idles perfect, starts first pop, temp never over 170, new manifolds and risers, I have also replaced inlet manifold gaskets and checked manifold for cracks.
No signs of water intrusion on plugs.
15% leak down on worst cylinder.
no water in oil but I have steam coming out of my breathers, block can't be freeze cracked aS I'm in Melbourne Australia.
Any ideas?

 

[Bt Doctur]

look for a broken exaust valve spring

 

[Scott Danforth]

A small amount of vapor is normal, and a byproduct of combustion.

 

[AMR]

There is s fair bit more than some vapour, there is water droplets dripping onto the inlet manifold.
And it only happens after full warmed up and run.
Can I ask how a broken valve Spring would cause this? Very interesting

 

[alldodge]

I'm leaning toward something is getting to hot. Suggest getting an IR temp gun and check for hot spots on the motor.

Was the intake gasket replaced because of this issue showing up or another reason?

 

[AMR]

Yeah I pulled the manifold to check it and the heads for corrosion and to have a general look inside, there's definitely been water in there at some stage, but I do know the manifolds and risers were leaking prior to me buying the boat.

 

[alldodge]

With signs of water previously, you might have a small crack which starts to leak after the water warms up. Its small enough that it doesn't mix with the oil and just steams away. Don't know just taking a guess. If you can find a hot spot on the motor this might narrow it a bit

 

[AMR]

Thanks for all your responses! I'll do some more digging. Cheers

 

[Scott Danforth]

A pressure test will help

 

[Bt Doctur]

I only mention it because I had a motor with that same condition and found a broken inner valve spring on a exaust. valve.