Major Blow By Issues

[Cptkid570]

1989 Mercruiser 3.0 Liter.

Long story short, the boat was running real bad at higher RPM's, I noticed some oil in the flame arrestor, so I did a compression check and my compression was great and consistent on all 4 cylinders.

So, I took it for another test drive to see if it was maybe carburetor or fuel pump related. I took the flame arrestor off (and the tube that connects the valve cover to the flame arrestor) and when I gave it some gas, oil absolutely shot out of the valve cover opening (where the tube to the flame arrestor attaches) like a geyser. I'm serious, Old Faithful from Yellowstone park came out of my valve cover hole. It seriously shot straight up in the air, hit the bottom of my engine cover and splashed all over the place.

With having great compression (I believe it was 150 to 155 on all 4 cylinders), what else could it be? Could it be a bad valve, cracked block, head gasket? What are some obvious things to look for if I remove the head?

I know a leak down test is going to be suggested, but this is a major issue. The reason why it is running bad is likely because of oil going into the carb.

Oddly, at the lower rpms, the boat runs perfect. I actually ran around 2500, maybe 3000 rpms and the boat ran very smooth and was on a plane, but if I sped up, it started to sputter (probably it hit the breaking point where oil came out of the breather tube).

Any suggestions?

Thank you everyone.

 

[Mischief Managed]

Re: Major Blow By Issues

Thinking the oil drain passages from the head to the block might be clogged, but it's just a guess. Sounds really strange.

 

[Cptkid570]

Re: Major Blow By Issues

Well, at least I could look at that by just removing the valve cover. In fact, it would be very messy, but I could take off the valve cover and see if oil is squirting out of a valve.

Could I do that?

 

[Don S]

Re: Major Blow By Issues

What is the oil level?

 

[Cptkid570]

Re: Major Blow By Issues

Oil level is good. It is not overfilled at all. If anything it may be a little low. Don't know if low oil amount would cause this. (wouldn't be more prone to happen if the engine had too much oil in it?)

Thank you so much for replying.

 

[Cptkid570]

Re: Major Blow By Issues

I was talking to a mechanic friend of mine and he said that my problem could be a stuck ring and that since I don't use the boat a lot, that it could've gotten some surface rust on it or something. He suggested that I put some Marvel Mystery Oil down the carb to help free it up. Does this make sense? Since the engine has been great, I'm not past thinking that it could be something that did suddenly get hung up... and I don't mind trying something like that before tearing the engine down.

Any opinions?

 

[Don S]

Re: Major Blow By Issues

If the rings were in bad enough shape that they needed MMO to free them up, then you wouldn't have good compression.

Like it or not, you need a leak down test to find out what the problem is.

 

[Cptkid570]

Re: Major Blow By Issues

Just to finish up this thread in case a future reader were to find it. My mechanical fuel pump was leaking gas into my engine block and therefore making my oil overfilled and very thinned out, allowing it to get extra pressure and shoot out of the valve cover.

I changed my oil and changed my fuel pump and all is good now. Yes, the failed fuel pump should've pumped the gas up that clear tube into the carburetor, but the tube had a block in it.

 

[Speakrdude]

Re: Major Blow By Issues

So the moral to this story is, "always check your clear tube"?