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Oil Blowby = frustration

Dan_az80

Dan_az80

Well-known member
Looking for some advice on a small issue I have. The engine is a 89' 350 (260hp merc) and is stock. I have yet to clean the spark arrestor, but I don't think that is the problem.

I have minor (and I mean very minor) oil blowby coming from the vent hoses from the valve covers and terminate at the spark arrestor. after a day of running, I have about a finger tip spot of oil sitting on the intake on both sides, right under the spark arrestor where the hoses terminate. I am anal, so it bugs the hell out of me that I have to wipe it up with a rag every weekend:brickwall:

Compression is good across the board, oil pressure is great across the RPM range, doesn't run hot, doesn't burn oil, oil still reading full, and there is no water in the oil either.

So after the long winded b.s. explanation, will installing breather caps with hose attachments (to retain the vent hoses/PCV hose) solve the problem?

This is what I am thinking about or something similar:
P4120446.jpg
 
What's the part number on those? I want to try them too.. Sorry I can't help your question but I have the same problem
 
illMATTic said:
Have you replaced all of the grommets and lines?
Click to expand...

Have not done that yet, I will have to give it a shot. I have to confirm, but I think one is just a grommet and elbow, and the other is a PCV with an elbow.

Is this oil drip a common thing with marine engines?
 
Dan_az80 said:
Have not done that yet, I will have to give it a shot. I have to confirm, but I think one is just a grommet and elbow, and the other is a PCV with an elbow.

Is this oil drip a common thing with marine engines?
Click to expand...

I have some oil on my valve covers just as you do. I am a noob when it comes to I/O's. I was thinking that all the rubber has shrunk up over the years.
 
I have a brand new 325 hp quicksilver gen+ crate engine in my boat with about 40 hrs on it my will have a little oil mist coming out of the vent line off the valve covers after i run it hard dont bother me a bit I run it pretty hard you got good water temp and oil presure run it.
 
My old motor before it threw a rod out the side had a lot of blow by I put a PCV valve on it and ran the line to the 1/4 inch connection on the back of the holley that motor ran about 8 psi of oil presure at idle she was a POS that the guy I bought it off of sold me a bill of goods on.
 
they have no PVC from factory until the newer ones, I change all mine over to reg car PVC's to carb or intake....Merc started it years ago on the 500HP keeps the engine much cleaner and vapors down...
 
What grade(Weight) y using? Do a cylinder leakdown test which checks the piston rings for wear. You can get the tester at harbor freight cheap. Some oil residue is normal... how many hours on the engine?
 
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