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Drive shaft bearings. How are they supposed to work?

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  • #1

    Drive shaft bearings. How are they supposed to work?

    Drive shaft bearings. How are they supposed to work?
    When I took my LU down I noticed I could wobble the lower part of shaft around a lot and I thought I understood why the two sealing was leaking water into gear housing. To me bearing arrangement is a mystery.
    Close to pinion there is a needle bearing taking radial load and no axial load. So far okay. Next bearing, in top of LU, a conical roller bearing turned so it takes axial load pointing downwards but load from pinion gear is pointing upwards. If there is no axial load on this bearing it is not stabile radial and shaft is wobbling around and seals are leaking.
    Only way it has worked as I understands, is if there a axial load on the upper shaft end keeping the conical bearing under axial load in all situations.

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  • #2
    I don't quite understand what you're asking, there is a bearing either end, when assembled in the case, the shaft is supported.

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    • #3
      cause you have not google searched helical spriral cut beveled gears.

      and that's not a conical bearing its a simple tapered roller bearing.

      yes its loose UNTIL its loaded.
      once loaded the bevel cut of the pinion and fwd gear pull the shaft down.
      unlike units that use a flat torrimgton bearing.

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      • #4
        Thank you rodbolt17 for a god explanation.
        I am a bit worried thou, in neutral or reverse the shaft will wobble and let water in through the seals. We will see.
        Everything inside looks fine only forward thrust "tapered" bearing had signs of discolouring from rust- nothing I could feel with my finger or nail, but I changed this bearing and hope thickness has so close tolerances I can keep original shims. Gear tooth contact patterns looks fine - the shining part of the tooth surface. I will put it all together and give it a go.
        To make it the Yamaha way a lot of tools are needed and I have to take it to a Yama shop and a lot of $$$$$ are gone. After al its a 27 year old motor.

        Thanks again för help.
        Bo Gunnar

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        • #5
          all that is needed to CHECK drive shaft shimming is a dial indicator and the back lash spec from the service manual.

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