blue smoke

[doubletrouble]

i have twin mercruiser 4.3 engines and 1 smokes blue at the start and then stops after a minute or less, is there something i can do to stop this? I dont know if this is common. My past boats have always had mag engines and i have never seen this. Any help is appreciated.

 

[Timayz]

I'm not a "boat" mechanic. I do know a "little" about engines though.
From the little bit you told me would bet on valve seals.(valve stem seals) Not difficult to change. Just time consuming...meaning extensive labor cost i'm sure if your paying someone. Parts would cost basically nothing. A few $$ I bet.
IF i'm right (have not checked your engine out so just assuming here) it's really nothing to worry about if it's not bad....
Basically when you shut it down a small amount of oil leaks through the seal and sits on top of the valve or piston.(depending on valve position) When you start it up it "smokes" till you burn off that oil. If it's severe and really smoking badly you can cause a carbon like buildup to occur (loss of HP) if it's not severe you could basically run forever like that and never hurt a thing.

 

[fwebster]

You will get more response, more details and better quality information if you provide information on year and model in your questions.

 

[Nehalennia II]

I agree with Frank. How old are your engines? How long has it been since a thorough tune-up? Also, do then engines run great other than your oil burning? Some Techron or Fuel injection cleaner in every tank may clean the valves enough to allow them to seat/seal better, but if you have some age on these old girls then your rings may be warn and allowing oil to slide on through enough to burn until they warm up.

 

[Gunn]

Timayz got it right; this is more of a general engine issue than specific. Common among all 4-cycle engines... Oil is getting into your cylinder bores and when the engine is started, it takes awhile to burn off, depending on how badly it is leaking in.

I have changed valve seals on a vehicle with and without removing cylinder heads before. You can get a tool that allows you to depress the spring from above to get to the seal and replace it.

 

[Alex D]

The 4.3 is no more than a 350 Chevy small block with two cylinders cut off. Interestingly though it is known for two issues that rarely plague the 350 and that is oil burn (blue smoke) and "dieseling", which is an engine running after the ignition was turned off and which is also often a side effect of oil burn and the subsequent carbon build up in the combustion chambers.