View Full Version : Detroit Diesel Smoke problem
" I have a pair of Detroit Diesel 6V92's in a 44 sportfisher. We have a chronic smoking problem in one of our engines. We have recently rebuilt the engine from the ground up. We simply can not get rid of the smoking problem (black smoke). We have made sure that the props are not fouled and or constrained, We have replaced the Turbos and made sure that the were turning the correct RPM, We have replaced the injectors, polished the fuel, cleaned the after cooler, re-plumbed the Airseps, checked the shafts and transmissions for anything that could be putting excessive load on the engine etc. We have installed Pyros on the exhaust systems and have found that the exhaust temperature is too high on this particular engine. Have we left something out? Has anyone run into this problem before. Does anyone know where I can find a really good troubleshooting guide for Detroit Diesels? Your help is greatly appreciated. Neal "
08-08-2003, 01:05 PM
" Neal, I have the same problems except with a different engine. Props were my problem. To much pitch and the props were actually to big. Cut them down and decreased the pitch and NO SMOKE and better fuel mileage.
" Is this engine getting enuf air. Restricted air filter or intake, clogged engine room vent????Something like that . try running with engine room hatch open? May be a prop problem as this previous post suggested. Kim "
12-30-2003, 05:12 PM
"By coincidence, I've just corrected a chronic black smoke problem with one of my ancient low block 671N's. Those 6V92's are also 2 cycle engines, and I suspect there is some shared designed.
I tried everything, so I thought. Air leaks.. all that stuff and nothing worked. I've just replaced injectors and in doing that I had a devil of a time timing the #5 cylinder injector. The danged thing just would not stand up tall enough for the guage. I loosened up the rocker arm assembly and bingo.. the plunger popped right up! It turned out that something is out of aligment on with the rocker arm posts and the two posts are too close together to allow free travel to all three rocker arms. I swapped the two posts and that freed everything up. I have six full power cylinders again.
Black smoke is always a rich fuel situation. Overload is the most common cause. But anything restricting air flow will do it too. Turbocharges, are always suspect, so too could be intercoolers, hoses, emergency stop dampers out of place or even a wrag sucked in an air intake. In my case it was overload, caused by a cylinder not putting out reasonable power. The rest tried to pick the load. A bad injector could do the same thing to you.
Air leaks in the air boxes will do it too. Injectors that are too large, possibly.
Maybe there's something in this that can help? Dang.. kick myself for never even thinking of the possibility that the rocker arms weren't moving properly.
Arthur... email@example.com ("")"
04-21-2004, 08:23 PM
I have 6v92's in a 1986 Chris craft. I am having trouble finding out who built the exhaust elbows for the boat. I know it is not Johnson and Towers. Can anyone help me with names of other companies that may have done the work. A name or phone number would help. The boat is down and the search is on for replacements.
04-26-2004, 08:22 PM
make sure you have no restriction in the exhaust
N. B. Whitten
12-30-2005, 06:29 PM
"I am considering the purchase of a powerboat with a Detroit Diesel Engine # 671, 485 HP, 2000 Hours. What could be my biggest challenges. The boat is 15 years old and I presume the engie was new in 1990. Any ideas will be appreciated."
"I WHOULD HAVE THE ENGINE INSPECTED BUY A QUALIFIED DETROIT DIESEL MECHANIC. LOOK AT THE BLOWER,INSPECT RINGS AND LINERS THR AIR BOX COVERS,TAKE A OIL SAMPLE. ALSO YOU CAN,T GET 485 HP OUT OF A 671."
01-16-2006, 09:13 PM
Sounds farmilar boat on the dock 44 ocean had a similar problem did just about everything you mentioned. Still had black smoke. I asked the owner if he had throughly checked the air intake from the outside. Guess what no more smoke. Seems a barn swallow decided to make nests in the air intake just inside the upper air box.
Please don't hate me if that is what it is after spending all that on repairs.
"SOUNDS LIKE EVERONE HAS COVERED THE POSSABLE CAUESES OF YOUR PROBLEM AND YOU HAVE CHECKED THEM OUT. NOW DO YOU KNOW THE HISTORY OF THE ENGINE? WAS THE ENGINE REBUILT BEFOR YOU GOT IT OR ARE YOU THE FRIST OWNER.AS STATED BEFOR BLACK SMOKE IS CAUESD FROM LACK OF AIR, RESTRICED AIR INLET. BLOWER,TURBO PROBLEMS.BLOWED INJECTOR TIP OR WRONG INJECTORS, WRONG CAMSHAFTS,ENGINE OVERLOAD. DOSE ENGINE SMOKE SETTING AT THE DOCK OR ONLY UNDER WAY IF SO WHAT RPMS DOSE IT START TO SMOKE."
just change after cooler in a 6v92 TA. we have steam coming blowing the relief valve on the air sep. is this normal until it burns off?
08-06-2008, 10:55 AM
I have 6v92ta's port engines oil pressure is 50 psi at cold start up and increases with rpm's to 75 psi. Have changed the pressure regulator and pressure relief valves. Problem still persist.Can anyone please give me an idea as to what could be the cause
08-07-2008, 10:34 AM
If any one could help me. I have a pair of 6-71DD TI's(450hp). My stbrd tank got water in it from the fuel guy. I am in the process of cleaning that up. My engine would blow blk smoke when the fuel/water separator would fill up with water. That is how I found out about the water problem. When I would drain the water and change the filter the smoke would be little but the engine would rev up to 1900 rpm's and more allowing the turbo to kick in. But my engine now smokes when I reach 1400-1500 rpm's (blk smoke). It does not smoke at low rpm's and it will not pass those rpm's. I have drained and changed the filters and even changed to racors. What could be causing this?
08-10-2015, 01:39 PM
i have a 1986 422 chris commander with detroit 671's water comes out the side to cool the motor. can i shut the valve off so water goes out the exhaust? would like to see if motors run quieter.
08-11-2015, 02:30 PM
I wish I could help. I have a 1985 CC 422 Commander with DD 6V92TA engines. I don't have any water coming from the side of my hull.
Not knowing what type of exhaust system you have, I couldn't make a recommendation as to whether to try it or not. I suspect it is directed that way because there isn't enough volume capacity in the exhaust riser. And, if that's the case, shutting off the the hull bypass "out" might stack up enough water to effect engine performance by introducing too much backpressure. Also, there would be the danger of water ingestion into the cylinders through the exhaust valves if you were to forget to open the valves before shutting the engines down.
These are noisy engines and I doubt you would experience the decibel reduction you are hoping for anyway.
Bottom line? If it were my boat I wouldn't try it.
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