Cummins Marine Diesel Repower Specialists Forums Cummins Marine Engines Black smoke at cruise – 6BTA M3 -370 hp

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    Topic
  • #78086

    Mike Uliasz
    Participant
    Vessel Name: Runnin' Down a Dream
    Engines: Cummins 6bta-M3 370hp
    Location: Mathews, VA
    Country: United States

    Port motor started smoking pretty good this weekend. Had slight black smoke a couple weeks ago. The boat seems over prop (2600 rpms wot at sea trail with slightly fouled running gear) to begin with. She had to work to get on a plane yesterday too. She got up to 2400 rpms and Cruised at 2200 rpms. 3000 rpms no load in slip. I did not run her without an air filter, but will try that next. The after-coolers have been serviced. Any additional next steps for a beginner B4 calling a professional? The motor was rebuild in 2013 with a new turbo and after-cooler, but it was not run much the last 2 years. The starboard motor seems much more responsive. 3300 no load in slip. Have a video, but to big to post. Thanks

Viewing 10 replies - 1 through 10 (of 10 total)
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  • #80469

    Mike Uliasz
    Participant
    Vessel Name: Runnin' Down a Dream
    Engines: Cummins 6bta-M3 370hp
    Location: Mathews, VA
    Country: United States

    Joe,
    It did solve the problem?. Both engines ran in sync nice this weekend. No smoke even when going up on a plane after trolling for a couple hours. Had a mechanic look over the engines Friday. Said my throttle cables are stretched so the throttles are not fully opening up. So that’s next on the list. But he didn’t calibrate the tachometer so I still need to get that done. He picked up on some wore steering parts the surveyor missed so making progress.
    Thanks

    #79162

    Mike Uliasz
    Participant
    Vessel Name: Runnin' Down a Dream
    Engines: Cummins 6bta-M3 370hp
    Location: Mathews, VA
    Country: United States

    Keeping my fingers crossed, engine ran fine under no load in the slip but need to test run. Been rough and windy,, and now I’m out of town thru the weekend

    #79121

    Joe
    Participant
    Vessel Name: Knot time
    Engines: 6BTA’s 370
    Location: Washington State, San Juan Islands
    Country: United States

    Mike,

    Did the refitting of the clamp resolve your black smoke issue?

    Joe

    #79027

    Mike Uliasz
    Participant
    Vessel Name: Runnin' Down a Dream
    Engines: Cummins 6bta-M3 370hp
    Location: Mathews, VA
    Country: United States

    Joe,
    Went back thru all the connections and the air hose coming off the bottom of the turbo had a gap, the clamp was partially off due to a bracket holding the metal air pipe never being screwed in to the back side of the motor.
    Thanks for the tip!
    Mike

    #78255

    Mike Uliasz
    Participant
    Vessel Name: Runnin' Down a Dream
    Engines: Cummins 6bta-M3 370hp
    Location: Mathews, VA
    Country: United States

    Thanks Joseph. I’ll do a double check on that.

    #78242

    Joe
    Participant
    Vessel Name: Knot time
    Engines: 6BTA’s 370
    Location: Washington State, San Juan Islands
    Country: United States

    Had a very similar issue with black smoke, low power and not able to get full rpm under load! Turned out to be a broken clamp between the turbo and aftercooler. Definitely worth a checking

    #78231

    Mike Uliasz
    Participant
    Vessel Name: Runnin' Down a Dream
    Engines: Cummins 6bta-M3 370hp
    Location: Mathews, VA
    Country: United States

    Thank you Tony for the guidance. #1 understood and #2 the next task on the things to do list. Appreciate the help.

    #78220

    Tony Athens
    Moderator
    Vessel Name: Local Banks
    Engines: QSB 6.7 550 HP
    Location: Oxnard, CA
    Country: USA

    Mike,

    You are all over the place and you need slow down & to listen to me..

    1) You have early 370 Diamonds ( CPL2208) rated 355BHP at a minimum at 3000 RPM, but need to be propped to reach an ACCURATE 3100-3150 RPM under actual use..

    2) Your tachs need to verified as your no-load WOT rpm should be over 3300 in neutral at the dock, engine at operation temp… Simple to test using 2600-2800 RPM as a reference

    3) After you understand #1 and accomplish #2, get your bottom cleaned and load your boat as you use it and go for a ride.. On thr surface of what you have posted you may be grossly over propped..

    4) If you are not reaching an accurate 3100 RPM or more and reach it easy loaded as you use the boat , props off and a trip to the prop shop is next.

    Tony

    #78215

    Mike Uliasz
    Participant
    Vessel Name: Runnin' Down a Dream
    Engines: Cummins 6bta-M3 370hp
    Location: Mathews, VA
    Country: United States

    Found the answer I was looking for on the forum, very helpful.

    One simple question, if I run the boat at 800 to 1200 rpm’s, displacement speeds till it’s pulled and get the props turned will it cause me any issue being over-prop? I have run less than an hour on a plane, more just shake down runs once the engines were at operating temp (180) after replacing the impellers and cleaning the heat exchanger and re-doing the after-coolers with the Seaboard kit. Had a brain fart at the sea trial with it hitting 2600 WOT and thinking WOT was 2800 based on the 330 hp specs. The running gear had a barnacle strike so was hoping that would close the gap. Planned on sandblasting the bottom to help reduce the weight. Not sure how much that will help.

    Engine serial numbers are 45408232 & 45407742. From another post it sounded like the water/fuel separators (Racor) should be upgraded. What setup would you recommend. It’s recreational use, probably 100 – 200 hours a year.

    Black smoke and soot on stern of boat

    #78087

    Mike Uliasz
    Participant
    Vessel Name: Runnin' Down a Dream
    Engines: Cummins 6bta-M3 370hp
    Location: Mathews, VA
    Country: United States

    Black smoke

    At 2200 rpms

Viewing 10 replies - 1 through 10 (of 10 total)

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