Oil seeping/leaking (2 questions in this one)

[bavedoggs]

Ive had a slight oil leak coming from my 3.0 liter since I bought it 7 years ago. The engine is very clean but without fail I always have a little bit of oil show up. I wipe it down and then its there the next time I check. Sometimes I think its coming from the top of the valve cover from the breather elbow and dripping down from there. I most commonly see it on the starboard side around and on top of the fuel pump. Its never much, always just a little but I find it obnoxious that I cant trace where it is coming from.

I also noticed oil seeping from around the manifold plug on the Port side. The Bolt that goes into the block is in tight, I have a hard time believe its leaking from there. However, it is at the very bottom of the engine so I'm curious if oil can be leaking/seeping from that same breather valve and slowly dripping down the port side as well. Please let me know if I'm missing something obvious.

 

[Bondo]

Ayuh,..... My guess is, it's from above,..... either the vent, or possibly the valve cover gasket,....

There's nothin' but water in the manifold, so the drain Can't leak Oil,....

 

[kenny nunez]

If you look closely at the mounting flange of the fuel pump there is a very small hole that is open to the crankcase that will push out some oil.

 

[bavedoggs]

The hole...that’s the one with the clear tube attached to it, correct? The tube is on tight and leads up to the flame arrester, so I don’t think it’s coming from there, but somewhere in that area.

 

[kenny nunez]

Look closer, the hole is about the size of a toothpick end. The plastic line is there should the fuel pump diaphragm rupture.

 

[bavedoggs]

Roger that, I'll take a look. And what does that pinhole do? Any idea? And is it normal then for oil to seep out of there or is it a sign that something (like a breather valve) might not be working correctly?

 

[kenny nunez]

All 4 cylinder engine crankcases have pulsations unlike the more multi cylinder versions. Not to be confused with “blow by” from worn piston rings. The pinhole in the fuel pump can be found on all mechanical fuel pumps. I am no engineer but they are probably there to relieve the pressure so that the return spring can keep the diaphragm to move freely and maintain a constant fuel pressure. The earlier in-line Mercruiser and OMC fuel pumps had the filter facing up with the pinhole lower and the seepage was not as noticeable, since the later style pumps are the opposite the seepage will collect around the pump.
It is also how water can get into the crankcase should the bilge plug still be in and the boat gets filled with rain water.
If anyone has a more knowledge on this I am always willing to learn something new.

 

[bavedoggs]

Wow, no kidding. There’s no way in hell I would’ve stumbled upon this info. Thanks

 

[Bt Doctur]

If your fuel pump has a pinhole and not the tubing going to the carb you have a AUTOMOTIVE fuel pump A barbed fitting goes there.
The vent hole(pinhole) is on all mechanical fuel pump, Its needed to allow the diaphram to to work.A cam pushes the diaphram up and down, the vent allows air into the pump to allow the rubber to flex. If you seal the hole the pump will not work.