Removing impeller Vospower

Discussion in 'Jet Drives' started by RocketDane, Jul 23, 2015.

  1. RocketDane
    Joined: Jul 2015
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    RocketDane Junior Member

    Hi
    We are having a problem removing the impeller of our Vospower 90 A drive. We have removed three screws from the plastic hub but cannot get the impeller out. We tried extracting the impeller with the screws by putting them in the three other, threaded holes but even though it moved backwards a bit it is still stuck on the axle.
    Can anyone help with tips and information?
    Cheers
     

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  2. baeckmo
    Joined: Jun 2009
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    baeckmo Hydrodynamics

    If you have got the impeller to move forwards on the nylon hub, then you pull the nylon hub backwards first separately without the impeller.

    The hub has a slot and if you press a wedge carefully into it, it will come loose easier. But note that you cannot pull the hub by pulling the impeller, since it is conical.

    One trick is to jam the impeller blades so the impeller can't move forwards, then use the pull-out screws to press the hub backwards (together with the wedge).

    Whichever, be careful, since the nylon hub will split if you use too much force.
     
  3. dsckeld
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    dsckeld Junior Member

    Thank you for your reply. I am working with @RocketDane on this boat, and I were afraid to apply too much force when I tried to free the nylon hub, which led me to believe that we maybe should remove the axle in order to free the nylon hub.

    The axle has some wear marks at the rear bearing location, so we will most probably remove the axle anyway to assess if the wear is okay or so execessive that we have to repair or replace the axle.

    We have read the "Operaton-Maintenance vosspower-90-100-115.pdf" oprations manual, but haven't been able to recognize all the stuff from our own drive, so ours is probably newer than the manual.

    From what I have seen, I expect the adjustment of the impeller on our model to be done by moving the nylon hub on the axle and lock it in the right place by tightening the impeller on the hub. Can you confirm this?

    Best regards,
    dsckeld
     
  4. baeckmo
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    baeckmo Hydrodynamics

    Nope, the axial position is obtained by shims between the fwd end of the hub and a shoulder on the shaft. If you open the handhole, you can probably see the shims.
     
  5. dsckeld
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    dsckeld Junior Member

    I don't recall seeing any shims. The axle has som play, and there were like 2,5 mm between the impeller and the wear ring. Am I looking for the correct play with the axle pushed forward, or should I try to adjust/repair the thrust bearings first?
    I expect the manual we have is OK in suggesting .15 to .5 mm play between wear ring and impeller.
     
  6. baeckmo
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    baeckmo Hydrodynamics

    Here's a drawing that shows the shaft components. The recommended radial play seem ok. There should be no noticeable axial play in the shaft, but you may have a radial flexing at the impeller position with the impeller off; that is no problem.

    If you remove the shaft, please observe that there are three lip seals in the main housing; two outside the grease hole and one inside (in addition to the seals in the bearing housing). Note that the bearings are inch sizes, standard available from SKF, FAG etc.

    A tip: the 90 jets were built to be able to run dry (for resque service et c). But if you don't need that, I recommend that you substitute the oil lubricated bearings in the stator with a normal cutless rubber bearing. It SHALL have a plastic/nonmetallic shell though (no bronze!), and you have to drill a 5 to 8 mm hole in the center of the stator hub to the rear, for the circulation of water. If the scars on the shaft bearing surface are not too bad, it will work fine with water lubrication.
     

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  7. RocketDane
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    RocketDane Junior Member

    Thank you for that, baeckmo :) We are continuing the work next Sunday now armed with the correct drawing and much knowledge.

    BTW the drive is in fact installed in a FRC, a Norsafe Mako 655, so you were right about the rescue services. Why do they need dry running drives?
     
  8. baeckmo
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    baeckmo Hydrodynamics

    If I recall correctly, some operating schedules demand engine starting to be possible already with the boat hanging in the hook.

    Til lykke!
     
  9. AndySGray
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    AndySGray Senior Member

    If it were me, I'd be tempted to find a piece of scrap plate and drill 3 holes to match the threaded ones, then use some suitable all-thread (tightened evenly) to pull the boss - you'd be pulling against the shaft end not pushing against the impeller.
     
  10. anthony goodson
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    anthony goodson Senior Member

    Kind Regards baeckmo
    It is of course a 90G not a 90A ,which is why his parts list may look a little odd.Not important in the area he is currently working ,but may be later.
     
    Last edited: Jul 25, 2015
  11. baeckmo
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    baeckmo Hydrodynamics

    Oh hello Anthony, glad to see your track here again! All well I hope?
     
  12. anthony goodson
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    anthony goodson Senior Member

    Hi baeckmo ,yes thankyou all is well with me ,and clearly with you too ,as prolific and helpful as ever.
     
  13. anthony goodson
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    anthony goodson Senior Member

    One of the best features of the 90g ,and only the G not the 90 is that if you detach the driveshaft to the engine ,and the bolts protruding from the front of the fibreglass casing,the complete thrust bearing /seal housing unit and shaft can be withdrawn as one lump through the rear of the jet.in fact all the working parts in one piece. You may have to pull quite hard as the perimeter of the bearing housing is sealed with a large o ring and they tend to stick.
     
  14. anthony goodson
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    anthony goodson Senior Member

    This might be useful.
     

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  15. RocketDane
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    RocketDane Junior Member

    Thank you, I am sure it will help.

    I never knew the drive is a 90 G. You learn something new every day unless you really try not to ;-)
     
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