Cummins Marine Diesel Repower Specialists Forums Cummins Marine Engines Gear clatter at idle… how to adjust idle rpm 5.9 6bta 315

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    Topic
  • #74164

    TallTailz401
    Participant
    Vessel Name: Tailz
    Engines: Cummins 6bta 315
    Location: Newport RI
    Country: USA

    Hey everyone,

    I’m having an issue at idle. Started happening a few weeks ago out of the blue. In gear at idle I’m hearing a very loud “clanking” noise. When I throttle up 50-100 rpm it goes away. Sounds like gear clatter, but I’m no expert. How do I adjust idle rpm and what is the safe maximum idle rpm to increase to?

    Cummins 6bta 315 M2 nippondenso

    Side note: since this problem started I noticed my shaft nuts are loose when I hauled the boat out. Prop slid right off, which has never happened before. I’ll be lapping shaft and prop to make sure I’ve got the proper fit. I’ve never had prop loosen before, so I don’t know why that would just start happening. Any advice would be greatly appreciated!

    Connor
    Newport RI

    1 user thanked author for this post.
Viewing 7 replies - 1 through 7 (of 7 total)
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  • #95483

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

    Gear rattle from an old “end of its life” torsional damper.. Think of it as a shock absorber on your car that is “done” or close to it..

    #95463

    gerryc
    Participant
    Vessel Name: Midnight Zulu
    Engines: Cummins QSB 6.7
    Location: Vancouver
    Country: Canada

    Rattle noise when decelerating at idle

    I have recently noticed a rattling/knocking noise when reducing to idle while the boat is decelerating on our
    Nordic Tug 37 (Twin Disc MG5061SC) The sound will go away if neutral is briefly selected and back into forward, orif the vessel decelerates enough so that the boat is not driving the prop. Could this be the damper plate and if so, should I just live with it until it gets worse. We have the boat on the market now, and although
    this noise is not that noticeable, it is likely to come up on a sea trial.

    #74204

    Jeffrey Fontes
    Participant
    Vessel Name: Reel Easy
    Engines: 6bta 330
    Location: NH
    Country: United States

    i wouldn’t touch the idle, they make noise if its a spring damper. its perfectly normal, now if its not a spring damper its worth looking into asap.

    #74191

    TallTailz401
    Participant
    Vessel Name: Tailz
    Engines: Cummins 6bta 315
    Location: Newport RI
    Country: USA

    Hey Jeff thanks for the reply. I’ve got a feeling it is the damper plate as well. I don’t want to pull tranny off as it’s a pain in the ass on my boat. If I adjust idle for now and pull tranny at end of season do you think I am risking any damage?

    Thank you

    #74190

    Jeffrey Fontes
    Participant
    Vessel Name: Reel Easy
    Engines: 6bta 330
    Location: NH
    Country: United States

    It’s more than likely a spring damper coupling if you have a zf and it goes away with throttle. It can be replaced. Call your local gear distributor with the sn or BOM # for your gear at the very least they can tell you what coupling your gear has/should have come w from the factory.
    If it’s an elestic coupling or centa if could be failing.

    As far as your throttle handle there should be an adjustment in the control head that has a friction screw to tighten up the movement
    -Jeff

    #74166

    TallTailz401
    Participant
    Vessel Name: Tailz
    Engines: Cummins 6bta 315
    Location: Newport RI
    Country: USA

    Great thank you so much tony! Should have also included that I’m having major throttle handle slip resulting in obvious rpm creep. Very annoying. I put a clamp on the cable which helped for a little while but problem is acting up again. Do I simply need a new cable? Spring adjustment?

    Thanks

    #74165

    Tony Athens
    Moderator
    Vessel Name: Local Banks
    Engines: QSB 6.7 550 HP
    Location: Oxnard, CA
    Country: USA
Viewing 7 replies - 1 through 7 (of 7 total)

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