Do Mercruiser have a PCV valve?

[bill 22]

I am asking because my Mercruiser does not. My valve cover just has a hose with no pcv valve straight to the air filter. It seems that an oily residue is forming on my air filter / breather and I just cleaned it three weeks ago.

Did Mercruiser start putting PCV valves on new engines?


1985 Mercruiser 3.0L M# MCM 140, SN: 6922598, with Mercarb

Thanks,
Bill

 

[Don S]

Re: Do Mercruiser have a PCV valve?

Nope, the 3.0L engines have never had PCV valves. That slight oil film on the flame arrestor usually discolors it, but it doesn't block it. If yours is getting clogged, you might want to do a leakdown test on your cylinders and see what's going on.

 

[bill 22]

Re: Do Mercruiser have a PCV valve?

It seems like it would be simple for them to add a PCV valve and helpful to keep that oil off of the flame arrestor.

I know PCV = positive crankcase ventilation but does that mean it keeps a small positive pressure on the valve cover if one is installed?

I did a compression test yesterday and I have the readings at home. The back cylinders were low. Something like 1= 115psi, 2= 95psi, 3= 75psi & 4= 55psi.


Thanks,

 

[Don S]

Re: Do Mercruiser have a PCV valve?

With those compression numbers you need an overhaul, not a PCV. You should be up in the 130 - 150 range.
You should be thankful it's even running.

 

[haulnazz15]

Re: Do Mercruiser have a PCV valve?

Yeah, I don't even see how the back two cylinders are firing with numbers that low, lol.

 

[bill 22]

Re: Do Mercruiser have a PCV valve?

Yeah, I was thinking that anything less than 90 would be low.

 

[Don S]

Re: Do Mercruiser have a PCV valve?

Anything less than 100 is low.

View attachment 97-25 Compression Test.pdf