Mercruiser 3.0LX repeatedly deformet air valve?

[skogveien60]

This forum looks massive. Looks like a powerfull source of knowledge.

Hi, I just bought a 1996 SeaRay 175 CB, with a Mercruiser 3.0LX and a Alpha1 outdrive. When I got it, it already had a deformed air valve on cylinder #2. Being a mechanic all my life (64 years), I have never seen a valve deformed like this. I ordered a new one, replaced it. Then I "grinded" all the valves a little. And I checked that they we?re tight and completely closed.

This was in the middle of the summer, and after a 4-5 hours running time. The new valve has become deformed like the previous one. Does anyone have any idea of what?s causing this?

The boat runs in Norway, in saltwater, but I flush through it with freshwater after every trip. I pull it up on my hanger after every use.

Have a nice day, everyone!

 

[chiefalen]

Re: Mercruiser 3.0LX repeatedly deformet air valve?

And when it happens you got no compression in # 2 right?

You pulled the spark plug? What it look like?

After you put in the new valve did you put a little gas on the valve to make sure it was sealed.

It's a leak down test.

I'm putting a new used head on mine. 4 banger like yours. We poured gas on all the valves, one was leaking down after about 5 minutes polished the seat and the valve. No more leak.

 

[skogveien60]

Re: Mercruiser 3.0LX repeatedly deformet air valve?

Hi again! Thanks for a quick reply!

Yes you are right, since it was deformed, it didn?t seal properly and there we?re no compression on cylinder #2. I polished the seats and valves aswell and performed a leak-down test with gasoline. And they all were sealed. The sparkplug was actually split when I got it. But I replaced it, and the store clerk gave me a plug with the wrong "heat value" (do you know what I mean, I do not know the english term)... so that one burned up aswell (overheated). Before my last trip I replaced all plugs with the correct ones, and they all seem okay.

 

[Don S]

Re: Mercruiser 3.0LX repeatedly deformet air valve?

Two things I would look at right off would be the carb running lean, and the timing.
Assuming you have the Delco EST distributor, are you putting the unit into base timing mode when resetting the timing, after setting, have you checked the advance timing?
Might also check the exhaust manifold and riser mating surfaces for errosion or possibley a bad manifold or riser. IF anything leaks water, it can damage the valves.

 

[skogveien60]

Re: Mercruiser 3.0LX repeatedly deformet air valve?

Thank you, I am not sure what a "riser" is in norwegian. Where is it and what does it do?

 

[enn858]

Re: Mercruiser 3.0LX repeatedly deformet air valve?

Hi Norway

The exhaust goes into the water cooled manifold and from there into the riser (it`s the knee you see on top of the manifold)


Water leak in the gasket betwean Manifold and knee is not uncommon - you should check it and also check how much corrosion you have in the exhaust manifold and knee - in salt water applications thay dont last more than 4-6 years unless flushed with freshwater after use
Your riser may look like this:

 

[skogveien60]

Re: Mercruiser 3.0LX repeatedly deformet air valve?

Thank you, i must say that people are very helpful here, and that is much appreciated.

When I got the boat there was a leak at the riser due to errosion. I took it out, went to a machine-shop and grinded the socket plate, and it is tight and sealed now. But the valve got deformet again after this.

If I want to check the manifold for any leaks I should robably use airpressure, right? Do you know how much pressure I should use? (It is actually my son who is translating here, maybe something gets lost in translation).

And if I there is something wrong with the timing and the distributor... it should be on all four cylinders, right?

Once again, thanks everybody for help and good advice.

 

[Bondo]

Re: Mercruiser 3.0LX repeatedly deformet air valve?

If I want to check the manifold for any leaks I should robably use airpressure, right? Do you know how much pressure I should use?

Ayuh,....

10 to 15psi is sufficent....

The deforming of the Valves is usually caused by a Lean condition,+/ or advanced timing....

Checking the timing is critical to Know that is set Right,....

Then move to the Carb, to make sure it's providing enough fuel....

The best way is to strip the carb down,, Soak the hard parts in carb cleaner,..
Blow out all the tiny passages with compressed air,+ then reassemble with the new parts provided with the carb kit....

Good Luck,+ keep Us posted........