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12v71 impellor change

Discussion in 'Technical Discussion' started by mysue, Dec 21, 2011.

  1. mysue

    mysue Guest

    Recently changed the raw water intake impellor on my stbd DD12v71. Not an easy job to get the new one in. **** thing has to literally be flattened out at the top to go in. Removing the top plate in the housing allows a much easier install for the impellor. But reinstalling the top plate is then a bear.
    Does anyone have a solution for this? It would be near impossible in a rough sea.
  2. dennismc

    dennismc Senior Member

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    Purchase the impeller puller it makes the job the way easier, take off the end plate and it's fairly easy from there,
  3. mysue

    mysue Guest

    Dennis
    Does the puller get the new unit back in? Pulling out the old impellor was no problem. Getting the new one in was the issue.

    Thanks
    Gary
  4. jhall767

    jhall767 Senior Member

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    Putting a lubricant on the impeller and housing always helps. I generally use dishwashing soap because it's handy and it won't harm the rubber. Warming the impeller will make the vanes more flexible and easier to install.
  5. dennismc

    dennismc Senior Member

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    I use a tie wrap on the end to squeeze the vanes then as it gets pushed in the tie wrap slides out along the vanes, that with some lube works real well. The first time you have trouble pulling one out you will wish had a puller.:)
  6. mysue

    mysue Guest

    Thanks for your replies gents. I'll get a puller.

    Gary
  7. Capt J

    Capt J Senior Member

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    A puller doesn't help get it in........I put a lot of super lube on the housing and shaft, and get it started and push it in.......you should lube the housing when putting an impellor in regardless. I've also taken a flat piece of wood and then tapped it in lightly with a rubber hammer, if they get stuck half of the way in......the trick is, once it's started and you start pushing it in.....try to push hard and get it in, in one shot......

    Getting them out, I've found that with the seacock off and the wear plate off, I spray a good amount of a light lubricant such as corrossion block all in the housing and center, then bump the motor twice and the impellor usually pulls out fairly easy......
  8. mysue

    mysue Guest

    injector timing

    My DD manual and I are seperated by 300 miles for the holidays. Does anyone know how many mm the setting is for timing an N70 injector on a 12v71?
    Thanks
  9. dennismc

    dennismc Senior Member

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    I would suggest very strongly, you consult a DD service dept. that info is critical to proper operation of the engine, any incorrect info obtained on an open forum could be very costly, not that there are not competent people here, but, for something that critical, go to the source.
  10. Capt Bill11

    Capt Bill11 Senior Member

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    +1 to all that. Just use one of the very large tie wraps and lube.
  11. CaptTom

    CaptTom Senior Member

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    And make sure you fold the vanes over in the right direction. If not they could break or be compromised when the engine is started.
  12. Capt Bill11

    Capt Bill11 Senior Member

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    FWIW, after all these years Tom I haven't found that to be the case. As long as the impeller is well lubed and you bump the engine over a tick to set the blades in the right direct, I've never seen an impeller have a blade issue from incorrect orientation of the blades at replacement.
  13. Caltexflanc

    Caltexflanc Member

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    One look at the old impeller before removal tells you which way to set the new one. I also like the tie wrap technique.
  14. Capt J

    Capt J Senior Member

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    I have also found that blade orientation doesn't have any effect on longevity or anything. I bump the motor over once or twice, then start it......all is well......
  15. CaptSteve

    CaptSteve New Member

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    You can also use a hose clamp to compress the vanes to get the impeller to go in.
  16. Garry Hartshorn

    Garry Hartshorn Senior Member

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    Exactly what I do
  17. K1W1

    K1W1 Senior Member

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    Hi,

    If you are completely stuck get a pair of verniers and measure the heights of the Injectors prior to pulling them out.

    A Timing Tool is not that hard to improvise as long as you know what height they should be.

    I once lost the tool on the way to a job and made a 1.484" tool out of a 2.5" bolt and two nuts. It took a couple of goes to get the nuts tight at what I measured to be correct.

    The engine fired up and ran fine all the way from Papeete to Panama with no Injector or other problems other than a few failed drive belts for a layshaft that drove too much for the belt size.

    I found the tool when I got back to NZ sitting on the floor of my car where it must have fallen when I was getting the rest of the stuff ready to go. I still have it although it has not been used by me since.
  18. saltysenior

    saltysenior Senior Member

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    round off [not much] of the sharp edge of the housing on the pump...
  19. mysue

    mysue Guest

    Not stuck at all, just time to run the verhead and adjust the injectors. I've always used a digital vernier to do this on other engines and gotten very good results. Was just curious as to what the hieght was on a 12v71ti. It's in my book, but I'm currently away from the boat. Again just curious as to what height was. Thanks, Gary
  20. rcrapps

    rcrapps Senior Member

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    There are some variables. 70s should be naturals. Advanced cam is your concern. I run my own racks and have the manuals with specs. But if you have never set your own racks, get someone who has, especially on a V. If your guessing, it's dangerous even with the tool.

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