4.3 Oil Smoke

[CountryME]

Hey guys, looking to see how common this is with others. I have a 2000 1900SR with the 4.3l mercruiser Alpha One Gen 2. Not exactly sure how many hours, but my best estimate is less than 300. I know that these motors are notorious for some blue smoke on start due to valve guide leakage, but I seem to get a whiff of oil smoke regularly when running at low speeds. The oil level is good and has not moved all season. Is anybody else experiencing a similar problem?

-JP

[pascavone]

only way to be sure is a compression check, as it will tell you if oil is getting into the top of the cylinders.

Sounds like you have one or two with bad compression.

[mcoffey]

Ummm, a compression test will not tell you if your valve seals are leaking, that will only tell you if the valves themselves are sealing to the head. If the valve seals are leaking they will let oil leak down the valve guide and into the combustion chamber or out the exhaust port and nothing more.
If you are not seeing any noticeable oil level drops, I would not worry too much about it unless it is smoking people out. Could it be that is running a bit rich and that is the cause of the smoke?

[mmwjr]

I agree with what mcoffey said.

JP, what color is the smoke? Blue is oil and Black is mixture. From what you described it sounds like either bad valve seals or guides.

[pascavone]

I would tend to think his rings are shot, hence low compression and the oil under pressure is coming from the cylinder walls, not the valve guides.

Sounds like the beginning of BLOW BY to me.

Valve guide are not under the compression pressure as, the valves hold that back.

Could be rich fuel, which is blue as you say, but more white smoke, and it smells.

Perhaps, you could be lucky and check if you have a leaking gasket dripping oil on the hot manifolds..... look for a wet spot.

[CountryME]

Thanks for chiming in guys. I have been working on motors since I was 12 and can assure you that it is oil smoke I am smelling. It is very little and I am probably the only one who is smelling it, but I was looking to see if anyone else had a similar condition. I'm not looking for diagnosis of the cause, I know all the troubleshooting steps I need to go through to determine if I have ring or valve issues. Appreciate the responses though.

-JP

[SRPATTON]

Don't forget to check the PCV valves.

SP

[mmwjr]

I had a 4.3 in my last boat and didn't have any issues. Since you are not using oil it can't be too bad. Worst case finish the season and ten hae te heads done.

May also be a leaking valve cover. But as you say you know your way around engines so I am assuming you hae already looked fo any leaks.

Pas blow by will puff a cloud all the time, leaking vavle seal or guides only puff at start up or changing engine speed. Oil at the vales is pumped up the push rod and flow down the rocker onto te vale stem to lube it. If the seal or guide are bad it runs down the stem into the chamber and burns.

[ss3964spd]

Originally Posted by CountryME

...I seem to get a whiff of oil smoke regularly when running at low speeds. JP

Not usually a leaking valve seal symptom.

Pull the plugs to see if it's confined to one cylinder or if it is across the board. Like others mentioned if the level hasn't changed then it can't be tooooo bad. Yet.