Excessive black smoke before and after turbos spool up

[Elias Baron]

Hi all. Been having this problem for a couple of years now. I have changed my fuel filters regularly and cleaned and pressure checked the aftercoolers. My motors are 6bta-m2 300 hp. It’s a 32 luhrs and props are 18×24 with a little cup. Not sure how much off hand. A well known prop shop tuned them beginning of last year. Seams like the turbos don’t really spool until 1800 plus rpms and some smoke clears up but I leave a trail of smoke under way.  A lot more than any other diesel around. I do have air seps and tried not returning I to the air cleaner with no difference. Could the exhaust have build up before the turbo not letting proper boost or not enough air in motor room for proper mixture? The boat had 454s when built and was retrofit with the cummins way before I purchased. I’ve owned the boat for 6 years now and didn’t have this problem for the first few seasons.  Any thoughts would help. Ty

Topic

[Clark Leighs]

 

Your boat is most likely overpropped thus the black smoke.

What guages do you have?   Boost, EGT ?   

Do you have a digital laser pointer phototach.  If not get one from Ebay or Amazon or the local auto parts store and use it to check the revs then engines can reach UNDER LOAD as you are now.    These things are accurate to +/-   about 2 rpm.

If you cannot reach the full RATED rpms for your engine + about 100 revs then you may need to repitch the props.     But get the tach and do the testing before looking at other potential areas of concern.     

 

By the way are you absolutely positive  that the air filters are clean?  Not just look clean but actually clean.

THis should be done with a clean bottom AND clean , undamaged props other wise it is a waste of time.

Also look through Tony’s Tips as he has written about exactly your problem.  But I will leave you to find it.

 

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