Click for Ocean Alexander Click for Cross Click for YF Listing Service Click for Nordhavn Click for JetForums

8V92Ti black smoke under load

Discussion in 'Engines' started by Capt Burt, Sep 5, 2021.

You need to be registered and signed in to view this content.
  1. Capt Burt

    Capt Burt New Member

    Joined:
    May 27, 2020
    Messages:
    8
    Location:
    Texas Coast
    Detroit 8V92Turbos J&T
    Engines rev to 2,000RPM NO PROBLEM, at slip=No smoke. But, underway black smoke??
    Prop wash shows one engine doing most of the work.
    I can get to 1/2 throttle, then no more RPM even though pushing throttles to max.
    I have:
    -Replaced fuels filters (to 20Micron)
    -Recharged/ Cleaned air filters
    -Purged Hyuantic lines
    -Added 80gal new fuel & 1 gal SeaFoam
    -Removed valave covers & checked for stuck injectors, purged/cleaned fuel lines.
    -Cleaned props.

    I am NO mechanic, but can generally fake my way around most little problems.
    Any input / suggestions would be deeply appriciated.
  2. RER

    RER Senior Member

    Joined:
    Jan 20, 2009
    Messages:
    1,532
    Location:
    Newport Beach CA
    Bad turbo
    bayoubud and Capt Burt like this.
  3. captainwjm

    captainwjm Senior member

    Joined:
    Aug 17, 2010
    Messages:
    296
    Location:
    Miami, FL, Cape Elizabeth, ME
    Bottom and props clean?
    Capt Burt likes this.
  4. Capt Burt

    Capt Burt New Member

    Joined:
    May 27, 2020
    Messages:
    8
    Location:
    Texas Coast
    Yes sir..
  5. Capt Burt

    Capt Burt New Member

    Joined:
    May 27, 2020
    Messages:
    8
    Location:
    Texas Coast
    Will ck that out. Thanks much!!
  6. Capt Fred

    Capt Fred Senior Member

    Joined:
    Jun 22, 2009
    Messages:
    319
    Location:
    Long Beach CA
    Without any more info or history, the turbo is the best guess. If turbos spin freely and tight bearing then intercooler would be another possibility. Measuring the turbo boost is not that difficult and would provide more info for accurate diagnosis.
    Capt Burt likes this.
  7. MYTraveler

    MYTraveler Member

    Joined:
    Dec 30, 2014
    Messages:
    63
    Location:
    PNW
    Could be bad injectors, as the presence of black smoke can only be explained by incompletely burned fuel. Unlikely that one bad injector would create your symptoms, so it would have to be multiple bad injectors. But unlikely that you would have multiple failures at the same time unless you have bad fuel (and filters) on a separate tank for the affected engine. Still, I would check the turbos first.
    Capt Burt likes this.
  8. Capt Ralph

    Capt Ralph Senior Member

    Joined:
    Sep 8, 2004
    Messages:
    12,647
    Location:
    Satsuma, FL
    When did this problem start?
    Overnight or thru the years?
    Any history?
    Black Smoke = Not Enough Air..
    Capt Burt likes this.
  9. rtrafford

    rtrafford Senior Member

    Joined:
    Jul 13, 2019
    Messages:
    1,578
    Location:
    Vero Beach
    Yes. Turbo, cooler....something either not producing or obstructing ramped up air requirements.
    Capt Burt likes this.
  10. Capt Ralph

    Capt Ralph Senior Member

    Joined:
    Sep 8, 2004
    Messages:
    12,647
    Location:
    Satsuma, FL
    Oh, Ensure shut down flapper is all open.
    Capt Burt likes this.
  11. Capt Burt

    Capt Burt New Member

    Joined:
    May 27, 2020
    Messages:
    8
    Location:
    Texas Coast
    Shut down flapper is open. Problem started several months ago, but only 20hrs ago or so. It's a live aboard that doesn't go out very often.
  12. Capt Ralph

    Capt Ralph Senior Member

    Joined:
    Sep 8, 2004
    Messages:
    12,647
    Location:
    Satsuma, FL
    Check air hose and clamps between turbo, inter-cooler & blower. Take air filters off.
    Check turbo for cracks and air leaks.
    As I expressed on another thread, Even if it feels good by finger, turbos may still not spin up.
    Could really use some air pressure readings on top of the blowers. Better to have air box readings also.

    Whole bottom clean???
    Capt Burt likes this.
  13. ArielM

    ArielM Senior Member

    Joined:
    Jul 8, 2010
    Messages:
    179
    Location:
    Los Angeles
    The no load on those engines is 2350 iirc. 2000 is quite a bit low. check turbos or after coolers.
  14. retiredguy

    retiredguy Member

    Joined:
    Sep 20, 2021
    Messages:
    82
    Location:
    InTransit
    Was wondering what you found? I am looking at a boat (68 foot 83000 lbs) with two of the same engines. Been advised to stay away from a boat with them as J&T really pushed hard to get the rated 735 H.P. so they wear out quickly and tend to be fuel hogs even at lower RPM cruising. Can I ask how many hours since the last major? Any other issues with yours?
  15. Capt Ralph

    Capt Ralph Senior Member

    Joined:
    Sep 8, 2004
    Messages:
    12,647
    Location:
    Satsuma, FL
    Update?
  16. Capt Burt

    Capt Burt New Member

    Joined:
    May 27, 2020
    Messages:
    8
    Location:
    Texas Coast
    Hey Capt Ralph...Verdict still not in. Actually I currently have the aftercoolers torn down, cleaned & ready to go back together..Ill know more after reinstall.
    Thanks...
  17. Capt J

    Capt J Senior Member

    Joined:
    Jul 11, 2005
    Messages:
    14,432
    Location:
    Fort Lauderdale
    Have you considered doing a compression check.....or easier still, start the motor and shoot the temperatures of each exhaust port of the exhaust manifold.
  18. Capt Ralph

    Capt Ralph Senior Member

    Joined:
    Sep 8, 2004
    Messages:
    12,647
    Location:
    Satsuma, FL
    I think more of lack of air or boost per fuel (rich), than low compression.
    Maybe, your thinking an over fueling injector or two.

    I was just thinking if this has the TA fuel modulator, stuck or over fueling.
    Starting to see more turbo issues on dock queens lately.
  19. Capt Burt

    Capt Burt New Member

    Joined:
    May 27, 2020
    Messages:
    8
    Location:
    Texas Coast
    No, i haven't though of those. Good idea!!
    I'll try it..
    Thank you
  20. Capt J

    Capt J Senior Member

    Joined:
    Jul 11, 2005
    Messages:
    14,432
    Location:
    Fort Lauderdale
    I've had 2 8v92's and 1 12v71 that blew tons of black smoke under load and all of them had a low cylinder......like 90 psi...... I've had dirty air filters cause it once, and turbos on a few boats also and dirty fuel filters or bad injectors on also. Being the boat sits and is so neglected by not being used, I'm willing to bet a dead cylinder. Which was the case with the 2 8v92's and they had 375 hours on them.