Oil out of the Vent Tube

[Blujay96]

I have a 1987 Mercruiser 3.0 in a rinker V180. There is a slight bit of oil coming out of the vent tube that comes out of the top of the valve cover and hooks to the side of the carb. What might cause this and should I worry about it.

 

[Bifflefan]

Re: Oil out of the Vent Tube

Check your PCV valve. It may be plugged.
How old is the motor? It may be blow-by. But probably the PCV.

 

[Knightgang]

Re: Oil out of the Vent Tube

PVC Valve. Common issue with automotive type engines....

 

[Blujay96]

Re: Oil out of the Vent Tube

The motor is a 1987. If it is blow-by. what can be done about it.

 

[bruceb58]

Re: Oil out of the Vent Tube

PVC Valve. Common issue with automotive type engines....

Its called a PCV valve and you won't have one on your engine. The reason you have blow by is because your rings are worn. Assuming your oil is not overfilled, there is nothing you can do about it short of rebuilding the engine.

 

[Knightgang]

Re: Oil out of the Vent Tube

Its called a PCV valve .

Common typo....

I figured all engines had one... Bad luck if it is the rings...

 

[Apollo75]

Re: Oil out of the Vent Tube

Why no PCV valve on some engines ?

OFM

 

[ziggy]

Re: Oil out of the Vent Tube

Its called a PCV valve and you won't have one on your engine.

agreed, it's just a crankcase vent. not positive crankcase ventilation. no valve for one way on most boats, though i do understand that some newer ones really have a pcv. but not older ones. i think worn rings too. ya could confirm with a cylinder leakdown test i believe..

 

[Blujay96]

Re: Oil out of the Vent Tube

How bad is it if the rings are worn. Is this something I can keep running the engine or should I do something about it now.

 

[Apollo75]

Re: Oil out of the Vent Tube

My old 1975 888 has a PCV valve --- just wondering why some boat engines do not have one --- I can not think of a reason not to have one

Every engine has blow-by --- they have gap-less compression rings now that helps --- just use your best judgement as whether it is too much or not and how the engine runs.


OFM

 

[bruceb58]

Re: Oil out of the Vent Tube

My old 1975 888 has a PCV valve

Where does the hose from this "Valve" run to? If it runs to the spark arrestor, its not a PCV valve. If it runs to the base of the carb(vacuum source) then it may be a PCV valve. There is no reason to have a PCV valve on a boat since it is basically an emisions device.

 

[bruceb58]

Re: Oil out of the Vent Tube

How bad is it if the rings are worn. Is this something I can keep running the engine or should I do something about it now.

Measure your compression. If you have low compression, could be a sign of worn rings and you will notice the decrease in your engine's power. No reason you can't keep running your engine. Does your engine burn oil?

 

[Apollo75]

Re: Oil out of the Vent Tube

My PCV valve has full vacuum at the base of the carb --- it is to vent the crankcase and remove / burn the crankcase blow-by --- it helps to remove moisture etc,. Does an engine good

Plus it adds a CFM or two to my little 300-CFM carb when my oil gets fuel in it.


OFM

 

[bruceb58]

Re: Oil out of the Vent Tube

The crankcase vents just fine without a PCV valve. Any moisture that is in there is released just fine without one as well.

Did your engine come with this? I don't see any mention of a PCV valve on the Mercruiser 888 parts pages.

 

[Bifflefan]

Re: Oil out of the Vent Tube

There is no reason to have a PCV valve on a boat since it is basically an emisions device.

The reason for a PCV is to help keep contaminents out of the oil, it has nothing to do with emmisions. They have been on engines since the 50's for sure and probably longer than that.

 

[bruceb58]

Re: Oil out of the Vent Tube

And you don't have the same contaminants on a boat engine. Have you noticed boats don't have air filters either? On an auto engine not only do you have the port where the PCV plus into, you have another port that goes to a filter. Obviously, you won't have that on a boat engine.

Curious what contaminants you are worried about.

PCV is an emissions device. California was the first to require them on cars in 1961.

 

[Apollo75]

Re: Oil out of the Vent Tube

IMHO -- boats should have their fuel vapors run to a carbon canister --- one way check valves --- sealed gas tanks etc.,

Bet it would help keep a lot of moisture out of the fuel --- and clean the air.

The catalytic converter needs to run hot --- I will get back on that


OFM

 

[Bifflefan]

Re: Oil out of the Vent Tube

Curious what contaminants you are worried about.

In any internal combustion engine there is some amount of air/fuel (burned or not) mix that slides by the rings. As the engine wears this will get worse. When this is absorbed by the oil it will start to break it down.
That and heat are the most common causes of oil breakdown.

California may have required them, but the manufactures were already putting them on before that for the reason they were intended.

 

[bruceb58]

Re: Oil out of the Vent Tube

Back to the topic...The OP will not have a PCV valve on his engine.

 

[alumi numb]

Re: Oil out of the Vent Tube

I have a 1987 Mercruiser 3.0 in a rinker V180. There is a slight bit of oil coming out of the vent tube that comes out of the top of the valve cover and hooks to the side of the carb. What might cause this and should I worry about it.

the only true resolve as stated for blowby is a rebuild, probably time anyway.
compression test for sure.
don't know nothin about a pcvv on this.
but coming out of the vent tube were?
maybe the tube has just degraded and soaked up thus seeping, happens.
maybe the vent line or port is plugged thus building pressure.
what grade oil are you using, could step up a grade "short term".
just about time to put her away any how so great rebuild timing.