Tips on rebuilding a velvet drive 72C

Discussion in 'Inboards' started by mongo75, Feb 22, 2008.

  1. mongo75
    Joined: Aug 2007
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    Location: Orange County California

    mongo75 Senior Member

    I'm installing a velvet drive in my project, and since I don't know it's history, I want to rebuild it (new seals, clutches) so I KNOW that I have a reliable unit, vice finding out the hard way 50 miles offshore....

    Could you guys maybe throw some tips my way, anything that might not be in the manual (which I do have) that might make it easier or faster to do, or any special tools I might need? I've never rebuilt a transmission, but I can do just about anything else.

    Thanks!
     
  2. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    The manuals are obsolete. The newest version is about 20 years old. The reverse clutch needs to have the clearance set correctly. Make sure the piston is bottomed out when you measure or the setting will be too loose. If you call the company, they are pretty helpfull.
     
  3. mongo75
    Joined: Aug 2007
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    Location: Orange County California

    mongo75 Senior Member

    Gonzo,
    Thanks for the insight. I haven't taken it apart yet so I'm not 100% clear on visualizing what you mean, but I do understand it. I'll take all the advice I can get on this one, so if you get bored one day soon, please feel free to write me a book! Otherwise, I'll see if the company has a new more up to date repair manual.
     
  4. Cuervo
    Joined: Mar 2008
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    Cuervo New Member

    Here is a website that has all the manuals.

    http://www.engine-cemberci.com/engine/sanziman/VELVET/VELVET.HTM

    I just rebuilt my 71c and it seemed rather easy. There are couple of clearances that need to be set. The clutch pack was the easy part. You also need a press and what they call specail tools to set a couple of bearings.

    The front pump gear needs to marked with a sharpie so you put it back in the correct way. I guess it wears to the pump housing and needs to go in the same way it comes out.

    The one thing I'm not sure of, and can't find in the books is if there is a specific way to put the pinion cage and output shaft assembly in. There are what look like oil holes in the housing and the shaft but I did not see if they need to line back up or if they were lined up in the first place.

    Good luck.
     
  5. Cuervo
    Joined: Mar 2008
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    Cuervo New Member

    I finally got some good weather and took the boat out for a test drive after rebuilding the 71C.

    It work out really well. The forward clutchs work really well and in neutral it just sits still. The reverse is working well too.

    The best note is that I no longer have a slipping in forward. The boat pulls very hard from 15 to 50 MPH. Its nothing like before!!!
     
  6. mongo75
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    Location: Orange County California

    mongo75 Senior Member

    Cuervo- did you replace the pump? How can you tell if it needs replacing??
     
  7. Cuervo
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    Cuervo New Member

    I did not replace the pump assembly. I did, however, replace the O ring and seal. They both came in the kit. I'm not sure what a bad pump would look like but the gears in mine look very clean without any abrashions or scaring. I would think that if it had worn down so much you would not have the line pressure needed to get forward or revers movement.

    In fact, the only items that look bad were the reverse clutch disc and metal bands. I did replace the forward clutch pack as well. I am very happy with my results and would do a rebuild again.

    I sent $200 on a shop press and less then $100 on the transmission parts so I'm sure I did ok.
     
  8. Stuff4Toys
    Joined: Mar 2010
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    Location: SW Florida

    Stuff4Toys 3Hulls.com

    I know it's been a couple of years since this post ended, but where is the best place to purchase drive rebuild parts?

    Thanks
    JOhn ><>
     
  9. mongo75
    Joined: Aug 2007
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    Location: Orange County California

    mongo75 Senior Member

    I bought all my stuff on ebay- its the same exact stuff you can buy at a boat store, but for about half the price. I used a manual and rebuilt it myself, works great!
     
  10. KingKudzu
    Joined: Sep 2010
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    Location: Charlotte, NC USA

    KingKudzu New Member

    Transmission Rotating in Neutral

    Just bought a 74 Ski Nautique with a 71C Velvet Drive transmission. In neutral, the transmission cotinues to move. Any thoughts on what the cause is and how to fix it?
     
  11. sdowney717
    Joined: Nov 2010
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    Location: Newport News VA

    sdowney717 Senior Member

    When I rebuilt my 72C I actually used a garden hose on the clutch piston oil pressure port hole to separate the parts.
    These velvet drives are very simple devices. I have rebuilt automatics from cars so I know how to do it.
    If it is still moving forward and truly in the neutral zone, it may be something like the clutch plates warped or apply piston not backing off all the way.
    If your somewhat mechanically minded, get a service manual and have at it.
     
  12. sdowney717
    Joined: Nov 2010
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    Location: Newport News VA

    sdowney717 Senior Member

    Reason I ended up taking this apart was I had a leak at the front. Turned out there is a large rubber ring and the cast iron face had some surface rust which prevented this from sealing. It was a big enough leak it had to get fixed. So I put in new seals and clutches and kept the old which were actually just fine.

    I have read the CG is actually looking in your bilge for oil and it they find it, they will fine you on the assumption you will pump it out when the bilge pump runs.
     

  13. Williamsotto
    Joined: Nov 2010
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    Location: Puerto rico

    Williamsotto New Member

    Thompson boat

    I have a 28 ft Thompson boat they said that was made by Rodney Thompson of Florida in 1977 and I have the hool and I what to rebuilding for fishing any information is going to be apprecited. In the expecifications of the boat or where can finded.
     
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