Wet Stacking... identifing and remedy

[MarioG]

last week I had some smoke coming out from inside the exaust blanket leading to the turbo. I uncovered the exaust manifold and noticed black oily looking fluid wetting the bottom of the flange connecting the exaust manifold to the exaust elbow leading to the turbo. I read here that this substance is probably not oil but a combination of unburnt fuel and carbon build-up do to long periods of slow operation of which we usually cruise around 1500-1800 rpms. if I read correctly, the only way to remedy this oozing exaust manifold situation was to run her up on plane for an extended period of time. on our way home we did just that. I wound her up to 2200 rpm and left her there for about 30 to 40 minutes. Lots of white smoke filled the air behind the boat but cleared up after about 10 mins. it also seemed to have stopped the smoking from the exaust manifold, but when i put back on the blankets it started to smoke again. as soon as I took off the blankets the smoking stopped. I guess the blankets are saturated eventhough they look fairly new but do have a brownish residue on the inside. I guess I'll replace the blankets but is this wet stacking a problem waiting to happen? should i change the oil sooner rather than later? is there any other way of cleaning up the exaust system besides running her up to full steam?

 

[doc g]

If the blankets are wet you have an exhaust leak . Wet stacking is the phenom you get inside the cylinders when there is not enough heat for complete combustion of the fuel , it causes dilution of the oil in the cylindres and premature wear . Running 15-1800 will never be a problem as far as wet stacking. It sounds like you have aleak at the turbo to riser area . Blankets should be cleaned /replaced . If there's enough oil I would assume it could catch fire if it has sufficient heat to light it off......Pat

 

[Boatsb]

I agree. 1500 RPM's should be more than enough to get them hot.

 

[SKYCHENEY]

Check the oil lines to and from the turbo. A small leak there can look like it's coming from the flange when it's not. It just runs down there and then burns off. You'll need to clean it all up and stop the leak before you have a fire.

 

[MarioG]

I checked and rechecked the oil lines and they are not leaking. I DID relpace a turbo before I left on our trip because it had a bad seal and was leaking. So, what I was seeing was infact oil in the exaust manifold flange smoking?

 

[Will]

I assume you're running Detroits.

Have you pulled inspection covers and looked in your airbox? Oil film in there is normal but if it's wet with oil you have another problem, perhaps clogged airbox drains, check valve or a bad blower seal, etc.

You mentioned white smoke when you ran them up. White smoke is fuel. Oil is usually blue. White would direct you to an injector or tune-up problem.

As others have said, 1,500 - 1,800 is in the normal operating range and shouldn't be a problem.

Will

 

[doc g]

Mario, if you just replaced the turbo it could that oil is just burning off from the install and/or the oil soaked turbo blanket. I don't know how much clearance there is in your ER but can you run it unblanketed and observe that it does indeed stop smoking after you heat it up good?If so then it's the oil in the turbo blanket that causing the smoke. I read somewhere on here that there is a way to clean them . They are not that expensive to replace either. Hope this helps..........................Pat

 

[Nonchalant1]

Do you have wet risers or dry risers? The pipe leading from the exhaust pipe to the turbo is the riser. Some are water jacketed and some are dry. Since you mention blankets, I assume that you have dry risers. In that case, the water may have gotten there from a leak in the water hose connection above it and the black or brown substance could be from a pinhole in your dry riser pipe? Dry risers can develop holes byhu rusting from the inside out. OEM dry risers were cast iron.

Doug

 

[Pascal]

Mario
afaik wet stacking is about unburned fuel in the cyls. if it's not an oil leak, then you have a leak on in the exhaust/turbo connection.

 

[REBrueckner]

Mario,
It's also helpful to state your engine type so we all know the main subject.

As you know, older Detroits might even smoke a bit when operated at 1800 RPM and be just fine for another twenty years. Ten minutes doesn't sound like an unreasonable period for some unburned fuel smoke before clearing at higher RPM.

If you have 160 degree thermostats you could consider replacing them with 170's...that's what I use in my 8V71TI's which I assume you have. Since you are in FLA 180's might be a bit warm if you want to run at higher RPM.

I had 180's in my starboard engine (which I did not know) and at 2,000 RPM or so in summer waters in NY/CT that engine would get to about 190 degrees which I did not like. It's just too close to the upper limits in my opinion. When I discovered the 180 thermostats and replaced them to match my port engine at 170's, occasional high RPM running results in temps about 180 degrees which I like a lot better.

As discussed on this forum many times, boosting RPM's from time to time after running at modest RPMs can be used to keep engines clean...I do that every five or ten hours of 1500 RPM running and initial light smoke clears within a minute or two.