Blue smoke

[doubletrouble]

I have twin 4.3 efi mercruiser engines with 155 hr on each. 1 of the engines emmits blue smoke at start and then stops, but will emmit blue smoke again after it sits for several hours. I have had the plugs checked and replaced. The technician has told me that he does not see anything wrong especially with the hours and it may be old gas (2 engines 1 tank..wouldnt that make both engines smoke) and I should not worry if it is not burning oil.. What else could be causing the smoke, could it be something clugged or am I and my boat neighbors seeing and smelling things.. help

 

[Presentation]

You have two problems. You have a poor technician and you have an engine problem that is causing blue smoke.

Blue smoke is formed by combustion of the engine's own lubricating oil. This can be the result of worn piston rings, valve guides, or oil seals. The oil can come from an overfilled air filter in the case of a diesel engine or excess oil in the crankcase.

Are you under warranty?

Keep a close watch on the dipstick. Do not go a full tank of gas with out checking the dipstick. Carry a extra coupe of quarts of oil onboard.

The above description is consistent with an engine that is starting to go however it could be other issues.

 

[Dave S]

We just had a similar discussion in this thread http://www.byowneryachts.com/forums/phpBB2/viewtopic.php?t=2513&start=0

Generally speaking when oil appears at start up and then goes away it is because oil is in the combustion chamber at start up. The most common cause for this type of problem is bad valve seals or bad valve guides or both. Oil will slowly seep into the cylinders with the engine turned off and then when you first fire it up you will see blue smoke. It burns off quickly and you never notice it again until the next cold start up. 155 hours is not a lot of hours to have either of these problems, but that's what I suspect may be the culprit. If you are still under warranty, then mention this to your technician and have him take another look at it.

 

[midway]

4.3L in the automotive side have been known for that problem for years. Just keep a check on the oil, if the engine is under warranty take it in and get it fixed. What you describe sounds like valve stem seals, if that is all that it is it will run for years like that. I had a 1987 Chevy Caprice with a 4.3L that I sold at 170,000 miles that still ran great, did not have to add oil between changes but when it sat for a while I had the blue smoke at start up but not after.

 

[NoWakey]

I'm just going to be a pile on here....
Yep, I have had 4.3's in vehicles, and in three boats. Valve stem seals. Don't sweat it, repair at your leisure.

Cheers,

Jim

 

[Gunn]

I responded to the original message you posted back in November of '06 here (http://www.byowneryachts.com/forums/phpBB2/viewtopic.php?t=1079&highlight=).
Your valve seals are letting oil leak into the combustion chamber once you shut the engine off. It may be one cylinder, or more. Not a big deal, just an annoyance, unless the oil consumption gets excessive. Valve seals can be fixed, either way with the cylinder head on or off the engine. If valve guides need replaced, then they need to come off. But I am surprised you are having this problem so soon. Possibly because the engine sat for a long period and the seals dried up?