Cummins 903

Discussion in 'Diesel Engines' started by Minusadegree, Dec 10, 2012.

  1. Minusadegree
    Joined: Jan 2012
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    Minusadegree Junior Member

    Does anyone know what a cummins 903 mated to a twin disc mg509 gear is rated for? Is it continuous duty? (Class A B C D)

    Kind of curious. As I was towing a 70' light barge at 1500rpm making 8knots when the the starboard gear let go. Broke right at the shaft in between the harmonic balancer and transmission side. Meaning I pulled the transmission and then had to remove the harmonic balancer from motors side.
     
  2. jonr
    Joined: Sep 2008
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    jonr Senior Member

    You may have been operating at a point where harmonic resonance was a problem (which is what the harmonic balancer reduces if it hasn't deteriorated).
     
  3. Minusadegree
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    Minusadegree Junior Member

    The gear is up in New Hampshire being repaired, is this something I should have these guys look at, meaning, check for balance and balance if needed?
     
  4. jonr
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    jonr Senior Member

    I would have them take a good look at the harmonic balancer and replace if there is any doubt.
     
  5. FAST FRED
    Joined: Oct 2002
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    FAST FRED Senior Member

    I would have them take a good look at the harmonic balancer and replace if there is any doubt.


    The unit has a service life , just because its installed it does not mean its OK.


    Replace it
     
  6. powerabout
    Joined: Nov 2007
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    powerabout Senior Member

    I thnk they are 295 if NA pleasure boat rating
    I have a few manuals let me dig them out and yes after a few years replace the balancer as FF says, a bad one can break a crank
    EDIT Strangley enough the manual says just measure the vibration damper concentric and out of round and use it?
     
  7. Frosty

    Frosty Previous Member

    You got any PTO?
     
  8. Minusadegree
    Joined: Jan 2012
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    Minusadegree Junior Member

    This actually makes a lot of sense. The gear let go, Felt like someone put it in neutral.
    I didn't notice any unusual vibration or hear anything. I suspect this was a time bomb situation.

    I'll just have the balancer replaced, I'm already into it for about 7k, doesn't make sense to have the problem a week later..

    The boat is an x-coast guard 41' UTB. The only PTO if you want to call it that, is the one on the front side of the motor, the water pump for fire fighting. But that's belt driven.
     
  9. WestVanHan
    Joined: Aug 2009
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    WestVanHan Not a Senior Member

    They can be up to 320 hp NA for marine use I believe,but that is peak and not continuous..I'd guesstimate 180-200 or so continuous rating.

    They turbo'd them up to 650 hp and for military use are/were in Bradley tanks, APCs I think, and some of the big trucks.
     
  10. jonr
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    jonr Senior Member

    2300 rpm max continuous I believe.
     

  11. Çemberci
    Joined: Apr 2007
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    Çemberci Senior Member

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