Why do I get oil/gases out of this hose up onto my engine hatch?

[Philster]

1996, Merc 502 Magnum EFI/MP. 320 hours.

See pic. Pic taken from top down. This is over the right bank of engine (if viewed from inside boat.

After running hard, the engine hatch/cover will have an oily residue on it. It is immediately above this hole (see red arrow).

Engine runs fine. Starts fine. Idles and shuts down fine. All fluids new. Tuned up, new manis/risers, new water pump kit/impeller, new belts.

Runs within max operating RPM range and a touch over 60 on GPS tach.

No complaints about the mechanics of the engine at all. Why the oily residue coming from this hole?

 

[HT32BSX115]

Re: Why do I get oil/gases out of this hose up onto my engine hatch?

Howdy,


It's probably a "tad-bit" of blowby.

Mercruiser doesn't use a PCV system (like my previously installed Hightech OMC 460 King Kobra!)

So you will probably get a little blowby of hot oil vapor that (like water vapor) will condense on cooler surfaces it touches. I can't tell exactly what that hole is but if it is connected to the valve cover maybe it should have a hose from it going to the carb. That way those "oily" gases will be sucked back into the engine.

Otherwise, you could route them to the bilge blower and let it blow them outside. the problem is that the inside of the bilge blower & hose will become an oily mess in time!


You should probably just junk that engine and get another one!!! (I'll be right over to take it off your hands!!!)


Cheers,


Rick

 

[Philster]

Re: Why do I get oil/gases out of this hose up onto my engine hatch?

Well, it is enough to notice, but not so much that it is alarming. It's annoying.

My initial thought was that the hose was the same size a PCV would sit it, but it looks like it is just going to blow out oil/vapor by design.

Oil level has hardly changed, but did drop maybe 1/8 to 1/4 (I am stretching it) of a quart since Memorial Day. Guess I put about 25 hours on her so far this year. Oil is dark, smells nice, but definitely along the same color/consistency of in-service car oil.

Last week, I dropped the dipstick down at least a half dozen times, and looked at the oil from every angle. Seems fine. If I asked 10 people, I'd bet five would say the oil level was fine. It was that close. Oil pressure is ok/fine.

If I give the hatch one good wipe, the residue is pretty much gone. I should post a pic of that.

Note: Not carbed -- Fuel injected. If you got that part right, I was considering letting you have the 502.

 

[HT32BSX115]

Re: Why do I get oil/gases out of this hose up onto my engine hatch?

On a fuel injected engine you probably wouldn't want any blow-by gases in the air intake. They'd REALLY foul a MAF or other sensor......

Note: Not carbed -- Fuel injected. If you got that part right, I was considering letting you have the 502.

Aw crap!!!I'm always a "day-late & a Dollar-Short!!

 

[TiredoleBoy]

Re: Why do I get oil/gases out of this hose up onto my engine hatch?

Why couldn't you get a filter to put in the hose to catch most of the blow by? Old carbuerated engines from cars had a small filter in the air cleaner that would work possibly .