Air cooled Diesel repower

Discussion in 'DIY Marinizing' started by TR7_FHC, Jul 17, 2009.

  1. TR7_FHC
    Joined: Jul 2009
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    Location: Cardiff

    TR7_FHC New Member

    Hello,

    Just beginning to start a new project, repowering a 22 foot Galion Yacht. The original inboard was a two stroke petrol (vire) engine which is beyond saving. Due to width and weight constraints it seems near impossible to fit any of the marine diesel engines currently in production.

    I do however have a Hurth hbw 10 gearbox and a yanmar L70 air cooled diesel engine. My plan thus far is to couple the engine and gearbox together (they are the correct rotation) with a bell housing and use a standard 4 inch coupling with elastomeric insert to join the shafts.

    Still in the design stage at the moment, any ideas on the coupling the engine to the gearbox would be appreciated, I know the correct way is with a damper device bolted to the engines flywheel that the gearbox splines connect to, however the flywheel is on the wrong end of the engine for this to work.

    I realise that I have significant work to do to make this system work including ducted cooling and sorting an exhaust. At present I plan to run an alternator and water pump from the engines front pulley and use a jacketed exhaust loop with water injection.
     
  2. mydauphin
    Joined: Apr 2007
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    mydauphin Senior Member

    And your question is?
     
  3. TR7_FHC
    Joined: Jul 2009
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    TR7_FHC New Member

    If anyone has any similar experience, particularly in coupling the engine to the gearbox?. and if the idea is sound or have I missed some major stumbling block?.

    my main concern is if coupling the engine to gearbox directly in this way will damage the gearbox due to the loading/unloading of the shaft during the firing pulse?
     
  4. BHOFM
    Joined: Jun 2008
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    BHOFM Senior Member

    BMW uses these in their drive shafts, might
    be some way to make a flange for your needs?

    [​IMG]
     
  5. CDK
    Joined: Aug 2007
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    CDK retired engineer

    Sorry but that is not properly phrased. The flywheel is where you take the power from, the other side of the crankshaft is the "wrong end".
    Some sturdy engines allow you to take considerable power from the shaft also, but it should never be the only engine load. The shaft may break from metal fatigue after only a few service hours and ruin your project.
     
  6. TR7_FHC
    Joined: Jul 2009
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    TR7_FHC New Member

    the design of the engine is similar to a lawnmower, with a shroud covering the flywheel (which has blades to act as a fan to force air through the engine.) the only output from the engine is the shaft. there is a pullstart mounted on the flywheel side of the engine.


    I have (hopefully) uploaded a photo of a slightly larger engine along with the gearbox that I intend to use. the engine i will be using is near identical but is 7hp instead of 10.

    I will do some more research on this area. many thanks for the advice.
     

    Attached Files:

  7. CDK
    Joined: Aug 2007
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    Location: Adriatic sea

    CDK retired engineer

    OK, I saw the name Yanmar and thought you were talking about a real engine. This yellow thing I know very well. I bought a brand new one (Chinese) for approx $300 and use it for an emergency generator. Because it is designed differently and has only one cylinder, the crankshaft can take the load from the bottom side. But my engine coupler already has been replaced 3 times. The crankshaft motion is such, that the mass of the generator rotor cannot follow such acceleration/deceleration, so the Woodruff key shears off after just a few hours. A rubber coupling and an extra bearing would be the solution but there is not enough room for these.
     

  8. apex1

    apex1 Guest

    Hatz Diesel!
    if you can afford it!
     
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