Bluish grey exhaust smoke

[Triskele]

This subject has probably been covered ad nauseum in this forum, but each situation is different and I wouldn't even know where to begin to look through all the threads on this site. I have two Johnson Tower 6-71Ti DD engines in a 1981 Hatteras motor yacht (so engines are 30+ years old). The starboard engine is throwing off a bluish grey exhaust plume when first firing the engines from a cold start. Also, does it when reving to higher RPM's. Still does it after cruising (warmed up) at low RPMs (1200rpm), but only when giving it throttle. Port engine does none of this (no smoking). Both engines run Delo 100 40 weight oil. Maybe only 10 hours of operation on new oil and filter change. Also added a gallon of Lucas treatment to each engine around the time of the oil change. Also, at around the time of the oil change, the mechanic who did the oil change also "set" the starboard rack. That was the only change to the starboard engine that was not done to the port engine. Other than that, all else was the same. Blue smoking did not occur prior to rack setting and oil change. The starboard engine smoking stops after about a couple of minutes once the rack stops "hunting" and the engine settles in to the idle rpms. However, when I give it some throttle (rev it up), the engine shoots off a plume of bluish grey smoke. This does not happen with port engine.

Additional information: Last time I had the boat out, the starboard (the one smoking) engine temperature was about 20 degrees higher than the port (185 vs 165). Also, the oil pressure for the starboard is 10 psi less than the port (25 (star) vs 35 (port) psi). The starboard engine has around 2900 hours and the port has around 2700 hours.

Lastly, the starboard engine has an aftermarket block heater installed. The port does not have a block heater. The port fires and starts up very easily. The starboard is harder to start and can take as much as 10 to 15 seconds of cranking to get her to fire. However, when I use the block heater, the starboard engine seems to start more easily. I have had this boat for nearly two years and the experience has been pretty much the same. The starboard is harder and tougher to start than the port. The previous owner told me to squirt a tiny bit of starter fluid in the intake when starting from a cold start. I assumed he knew what he was talking about since he previously ran a diesel truck dealership. However, my mechanic recommended against doing it so I don't and haven't continued with this practice.

Thanks in advance for any helpful advice or input.

[bostonhatteras]

I had a burned valve once and that is the color smoke it produced. I checked out all the cylinders by shorting the injectors one by one until I found the bad cylinder and the smoking stopped while the injector was shorted. Not saying that is exactly what you have but blue smoke is oil and white is unburned fuel. In mine the unburned fuel was washing the cylinder walls and making the bluish smoke. I deactivated the cylinder via injector adjustment and finished the season on 7 cylinders. Got to love those detroits because no other diesel can pull that trick!

A block heater on one engine? Sounds like the previous owner was milking it for all the hours he could get. Did your pre purchase survey pick up on any of this?

[osprey]

Black smoke is non burnt fuel (either too much fuel, or not enough air), white smoke is generally steam and bluish smoke is burning oil, one possible cause is leaky blower seals. to check; remove intake from blower, start engine and shine a light across the top of blower, if your see a mist then you have a leak (also, if the rotors of the blower are wet, this would indicate oil coming in with your air charge). Be careful not to allow anything to fall into the blower.

good luck,

Pete

[Genesis]

Sounds to me like a tired engine; blue smoke is oil as noted, and there are a number of places it can be coming from. With the poorer starting performance on that side (how cold is it when you're running into 10-15 seconds of cranking to get it to fire without the block heaters?) you could be anywhere from decently worn to REALLY worn, in which case the oil consumption could be from worn oil control rings allowing carry-up into the airbox and subsequent burning of the oil.

Detroits will run surprisingly well for a long time with very low compression, but they get real hard to start when cold and start smoking like this.

[bostonhatteras]

Black smoke is non burnt fuel (either too much fuel, or not enough air), white smoke is generally steam and bluish smoke is burning oil, one possible cause is leaky blower seals. to check; remove intake from blower, start engine and shine a light across the top of blower, if your see a mist then you have a leak (also, if the rotors of the blower are wet, this would indicate oil coming in with your air charge). Be careful not to allow anything to fall into the blower.

good luck,

Pete

black smoke is partially burned fuel. white is unburned fuel. Engines that are old and worn out and smoke white until warm up are pushing unburned fuel out the exhaust. the cylinders aren't warm enough to burn it. Engines that are ok but are being pushed too hard put out black smoke

[Triskele]

I had a burned valve once and that is the color smoke it produced. I checked out all the cylinders by shorting the injectors one by one until I found the bad cylinder and the smoking stopped while the injector was shorted. Not saying that is exactly what you have but blue smoke is oil and white is unburned fuel. In mine the unburned fuel was washing the cylinder walls and making the bluish smoke. I deactivated the cylinder via injector adjustment and finished the season on 7 cylinders. Got to love those detroits because no other diesel can pull that trick!

A block heater on one engine? Sounds like the previous owner was milking it for all the hours he could get. Did your pre purchase survey pick up on any of this?

Not sure I understand what you mean by "milking it for all the hours he could get." Do you mean he ran the engine beyond it's scheduled maintenance or life? Not sure what you are suggesting. Can you clarify your point? As for the survey and surveyor, don't get me started. A complete waste of time and money. My first purchase. Won't make the mistake of hiring a surveyor if I have another...purchase.

As for your issue (burned valve), did it only produce smoke on start up or was it persistent during operation? Mine only occurs during start up and then stops after a minute or two. Possibly the beginning of something more serious as with what you experienced. Ergo my reason for trying to get on top of it early. Thanks for your feedback.

[Triskele]

Black smoke is non burnt fuel (either too much fuel, or not enough air), white smoke is generally steam and bluish smoke is burning oil, one possible cause is leaky blower seals. to check; remove intake from blower, start engine and shine a light across the top of blower, if your see a mist then you have a leak (also, if the rotors of the blower are wet, this would indicate oil coming in with your air charge). Be careful not to allow anything to fall into the blower.

good luck,

Pete

Thanks Pete! I will give this a try. I have some suspicion that the blower seal may be the culprit. Back in February, prior to the blue smoking problem, I tried to start the starboard during cold weather (maybe 45-50 degrees ambient temp) without first plugging in the block heater. Engine wouldn't fire and engine room filled up with smoke from blower. Leads me to think that there might be a problem with the blower seal. Will follow your advice and take a look.

[Triskele]

Sounds to me like a tired engine; blue smoke is oil as noted, and there are a number of places it can be coming from. With the poorer starting performance on that side (how cold is it when you're running into 10-15 seconds of cranking to get it to fire without the block heaters?) you could be anywhere from decently worn to REALLY worn, in which case the oil consumption could be from worn oil control rings allowing carry-up into the airbox and subsequent burning of the oil.

Detroits will run surprisingly well for a long time with very low compression, but they get real hard to start when cold and start smoking like this.

Hmmm...since this engine has almost 3000 hours, much of what you say is definitely possible. I was told the previous owner was meticulous about maintaining this boat and engines and had a good mechanic. Given some of the other problems I have found with this boat, I am suspicious and as well less than pleased with the findings (or in my case, lack thereof) of the surveyor (who has proven to have been virtually useless). Oh well, welcome to first time 30+ year old yacht ownership. Sorry, I digress. Back to my smoking problem. I think I now get bostonhatteras point that the previous owner may have been using the block heater to "milk" the engine.

[Triskele]

In addition to this forum, I belong to a Two Stroke Detroit Diesel forum at Yahoo.com. I posed the same question there as here regarding my starboard engine blue smoke issue. Below is a comment from one of the members. I thought it was informative. It also included a troubleshooting guide for exhaust color. Thought members here might find it to be beneficial. Information and comments appear to be consistent with the advice received here on this forum. Thank you all again for taking the time to offer insights and share your wealth of knowledge. This site is the best!

"Here is some information about smoke color and what it might possibly indicate:
If you just had an oil change, MAKE SURE the oil is not over full in that starboard engine FIRST!
Another bit of advice..... Anytime you run two or more engines that perform together such as in your motor yacht, it is EXTREMELY important to have both engines functioning in synchronized harmony.....i.e., both engines should be tuned together and perform at the same output level (Torque or HP) for a given rpm. If you run the rack on one, then you should do both; if you change injectors on one, then do them both.....and have a QUALIFIED mechanic do your work and your adjustments.....power matching is important for performance and for the lives of your equipment as well. In boats especially, due to the fuel docks, be sure you are getting good quality fuel and that there is no condensation in your tanks from sitting. Keep your fuel system clean, your AIR AND FUEL filters clean and the engine and fuel systems properly adjusted."

Hope that lends some insight!
Keith,
Cairo, Egypt
The Answer is in the Smoke

We can generally understand what is wrong with a diesel engine by the color of smoke emitted from the exhaust. There are three basic colors - black, white and blue.

Black Smoke

This is due to a air to fuel ratio imbalance, either the fuel system is delivering too much fuel into the engine or there is not enough clean air (oxygen ) a few things to look for:

· Faulty injectors (injectors need attention at about 100.000 to 120 000 miles)

· Faulty injector pump

· Dirty air cleaner

· Turbocharger or intercooler faulty

· Problems within cylinder head, valves clogged up due to faulty EGR (exhaust gas recycling unit)

White Smoke

Normally means that the fuel injected into the cylinder is not burning correctly. The smoke will burn your eyes.

· Engine/pump timing out

· Fuel starvation to the pump causing the pumps timing not to operate correctly

· Low engine compression

· Water/petrol in the fuel

Blue Smoke

The engine is burning engine oil

· Worn cylinders or piston rings

· Faulty valves or valve stem seals

· Engine over full with engine oil

· Faulty injector pump/lift pump allowing engine oil to be mixed with the diesel

[Tim Powell]

yOU DO NOT WANT TO HEAR THIS!!! I left Beauford SC all well arrived at Charleston SC bridge which had to wait for it to open bluish gray smoke appeared at iddle, Bottom line a valve broke and part of it went to the turbo 2500$ to rebuild this just the beginning Fifty two thousand dollars later thats right 52000$ both 892'2 rebuilt they currentely have less than 10 hours and no black.bluish, green. red. purple. yellow no nothing eaven the steam a little problem is fixed. THAT IS THE BOTTOM LINE. Your engines are tire with 3000 hours this is my second go round my first was with 692s in a 45c.
You may aswell realize the fix is a rebuild. The information you got from the previous post are all correct. They just neglected to tell you the BOTTOM LINE FIX.
Welcom to the boating world it is fun and expensive.
Tim