Oil Leaking from Fill/Breather Cap

[Amphibiographer]

Hi everyone!
There is oil on the engine all around the oi fill/breather cap, it seems to blow out from the breather holes, is this normal? Do I need a new cap with better filter inside?
Why would there be holes in the fill cap in the first place seems strange to me!?
Terry

[Dave Neptune]

What is your oil level? Other than to much oil in the pan it would be blow-by from the rings. Another contributor could be to much timing (to advanced) or even a stuck c-advance.

Perhaps a PCV set up may help too.

The holes are to "ventilate" the crankcase.

Dave Neptune

[Surcouf]

worst case could be that something else than oil is raising the level... no mayo on the dip-stick?

[ndutton]

Mechanical or electric fuel pump?

[Al Schober]

Definitely check the oil level! If the oil level is OK, I'll have to REALLY start thinking. If the oil level is high, then we can attack that issue.

[Amphibiographer]

Definitely check the oil level! If the oil level is OK, I'll have to REALLY start thinking. If the oil level is high, then we can attack that issue.

Oil level is fine.

[Amphibiographer]

worst case could be that something else than oil is raising the level... no mayo on the dip-stick?

no it looks good. And oil level is fine!

[Amphibiographer]

What is your oil level? Other than to much oil in the pan it would be blow-by from the rings. Another contributor could be to much timing (to advanced) or even a stuck c-advance.

Perhaps a PCV set up may help too.

The holes are to "ventilate" the crankcase.

Dave Neptune

hmmmm none of those sound good!! We've recently timed the engine but it's still coming out some .

[Marian Claire]

As mentioned by others it sounds like blow-by to me. Did this start suddenly or has it slowly gotten worse? The options are to rebuild the A-4, add a PCV to help control the blow-by or just live with it. Think about how you plan to use the boat. Quick trip out of the marina? Then you may get by with just running the fan to clear the gasses when you are under power. PCV will help but has its own issues. Going cruising? May need to rebuild.
Dan
S/V Marian Claire

[Dave Neptune]

Since the oil level is fine it eliminates a lot of possibilities.

Try backing the timing off a few degrees, it should help by controlling the cylinder pressure when the fuel is burning. If the timing is to advanced the engine may feel more responsive BUT this causes the fuel to have burnt (expanded) to fast so as the piston gets to the top of the stroke the cylinder pressure is to much and forces some gasses past the rings. Backing the timing off will reduce the shock and produce more torque while reducing the ring loads. The shock I refer to is commonly called pinging but in a low compression engine like this it is seldom audible. Also premium fuel will not help as it burns to slow for this low of compression!!!!!!!

Do a "dry" compression check then a "wet" compression check. This will give some info on ring wear.

You did not state whether or not the "blow-by" started abruptly or gradually. If gradually it could be just plain ole wear and tear. If it was an abrupt change you may of broken a ring which is not real common.

Dave Neptune

[Al Schober]

OK, oil level good.
Another question - are you getting fumes in the cabin?

[Amphibiographer]

OK, oil level good.
Another question - are you getting fumes in the cabin?

Yes, we're getting fumes which I thought were exhaust fumes! Trying to find a leak in the exhaust system.

[Amphibiographer]

Since the oil level is fine it eliminates a lot of possibilities.

Try backing the timing off a few degrees, it should help by controlling the cylinder pressure when the fuel is burning. If the timing is to advanced the engine may feel more responsive BUT this causes the fuel to have burnt (expanded) to fast so as the piston gets to the top of the stroke the cylinder pressure is to much and forces some gasses past the rings. Backing the timing off will reduce the shock and produce more torque while reducing the ring loads. The shock I refer to is commonly called pinging but in a low compression engine like this it is seldom audible. Also premium fuel will not help as it burns to slow for this low of compression!!!!!!!

Do a "dry" compression check then a "wet" compression check. This will give some info on ring wear.

You did not state whether or not the "blow-by" started abruptly or gradually. If gradually it could be just plain ole wear and tear. If it was an abrupt change you may of broken a ring which is not real common.

Dave Neptune

We timed it for the highest revs as per Don Moyer's recommendations in his video so we'll try backing it off some. I think a gradual start, oil has been building on the engine for awhile and we're getting what I thought was an exhaust smell in the the cabin and engine compartment! It's been like that for months.

Not sure what wet or dry compression check means?

Thanks so much for this info Dave, much appreciated!! We'll try backing off the timing and let you know what happens.

[Amphibiographer]

Mechanical or electric fuel pump?

Mechanical.

[Dave Neptune]

Do the dry test first then the wet test. Either remember to shut the key off or remove the ign hot lead from the coil. Leaving the coil (ign) on can fry the coil be carefull.

Dry compression check. First remove the plugs and be sure the batteries are charged fully, then set the throttle for wide open full throttle. Now do the check and record your findings. Best to do each cylinder twice.

Now it is time for the wet test. The wet test is the same procedure but you spray some WD-40 or lube oil into the spark plug hole and do the test with the oil. Again record your findings and test twice.

The wet test will let you know about the rings as the oil will seal them a bit and yield higher compression values if the rings are leaking.

If the exhaust is leaking you will need to address that and it is not as daunting as it sounds but very important to safety.

When setting the timing via "power timing" ALWAYS back it off from max a few degrees. The engine will like it and run much smoother. Or you can go through the process to find TDC and add marks to the flywheel or accessory pulley. Then you can be sure of the proper setting.

Dave Neptune