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Thread: VelvetDrive with 2.57:1 Ratio??

  1. #1
    MoJetBoPar
    Just scored on an old V-drive with a 2.57:1 ratio velvet drive.
    I'm new to this style of drive and don't know the ratio in the water-cooled Casale or propeller size (it's a 3-blade).
    What would be a good v-drive gearcase ratio to work with my velvet drive (top speed is more important than torque)?
    Any recommendations on a propeller size?
    Is this arrangement more of a ski boat thing than a top mph hot boat?

  2. #2
    Stab-n-Steer
    MoJet,
    2.57:1??? Dude, are you sure? That means at 6000 RPM you will have a shaft RPM of 2334. Velvet Drives do come in reduction ratio drives but you don't want that in a v-drive!!! To further explain, you would need a 257% overdrive in the v-drive just to get back to 1:1!!! ie., the motor and prop turning the same RPM... Normally in a v-drive you'll want 10 to 30% overdrive or even more for racing applications. The reduction drives are used on tow and work type boats that spin a very large diameter prop for torque and pulling capacity. They are also used on old style cabin cruisers that have water-displacement hulls (non-planing).
    The reduction ratio velvet drives have a planetary gear reduction box and are longer in length than the 1:1 drives. The only thing I can imagine is that your drive has been modified to lock up the reduction drive and it is really 1:1... But why not use a regular 1:1 drive to begin with?
    S&S
    [ August 15, 2002, 03:45 PM: Message edited by: Stab-n-Steer ]

  3. #3
    MoJetBoPar
    Thanks S-n-S,
    I know what you're saying. Even though I'm new to the V-drive ownership, I've seen people mention the ratio's in the range that you mentioned.
    BUT, that's what the tag said on the case of the velvet drive. I hope your right, or I'll be looking for another velvet drive unit.
    How do they "lock-out" that ratio that you spoke of?

  4. #4
    Stab-n-Steer
    MoJet,
    After thinking about it, the reduction unit bolts onto a standard 71C & 72C boxes with an adapter plate. Maybe someone removed the reduction drive and replaced it with standard output housing and flange but the ID tag still indicates the reduction box. One way to tell - measure the length of the velvet drive from the face of the bellhousing (where the tranny bolts on) to the output flange (where the driveline bolts up) It should be 10 1/2"...Hope this helps.
    Also, give us more description of the boat - Hull make, length, motor, HP, etc. If she's already got a velvet drive in 'er than she's more of a ski boat than a MPH boat.
    S&S
    [ August 15, 2002, 05:20 PM: Message edited by: Stab-n-Steer ]

  5. #5
    MoJetBoPar
    Thanks again, S-n-S!
    I looked at the velvet drive unit and the tag says AS4-71C. But, I didn't see your response until just now and I'll measure the unit tomorrow.
    The hull is an 18' 68 Rayson Craft Flatbottom with a 440 Chrysler BB Wedge and it looks like the Casale unit is about a 1.15:1 ratio. The motor is a 69 with closed chamber 67 cylinder heads and it sounds aggressive at idle, I'd guess 400-450 HP at best.
    I'm hoping your hunch is right and the velvet drive runs at 1:1. Maybe it is just a domesticated version of a ski/drag boat, it has a single lever cavitation plate system too.
    I'll post what I find tomorrow. Thanks again.
    [ August 15, 2002, 06:13 PM: Message edited by: MoJetBoPar ]

  6. #6
    DaveA
    MoBo,
    I suspect that the reduction box was removed, too.
    All this yakking about ratios you've read is about the v-drive itself. Boats such as yours (and mine, too) run an overdriven 'final drive ratio' if you will. 1000 engine rpm into the box equals 1000+ propshaft rpm outta da box. I've got my own way of figgering overdrive ratios to to about 1-2% without cracking the case open that involves a protractor and a level. I'll expound if so directed.
    If your transmission's a 71-C, it's a little lite for that application, but apparently it's lived this long in the Rayson, so keep it. The heavier box, the 72-C, is the tougher of the two, with more clutch plates for one thing. Really a better choice if you're inclined to stomping it more than occasionally
    They're fairly simple boxes, and anybody that's done alot of old Ford/Borg-Warner transmission work will recognize the guts in it right away, so don't get tied up with someone that thinks rebuilding them is anything real special- or overly expensive, like the tournament ski boat dealers around here that can't wait to get a piece of someone with tranny trouble. They've all salivated at the big $$ that the Mercruiser guys get for cracking open Alphas and Bravos, and want some similar action for themselves. But I digress....
    Try this link to learn more about your tranny:
    http://www.boatswainslocker.com/prod...ive/71_72.html
    I've got a couple of other sites on the 'net, such as www.marinetransmission.com on the other laptop, and will try to remember to post them next session on it.
    My 72C is sitting on the bench right now being disassembled slowly but surely.
    Hope all this crap helps... this is a Full-Service V-Drive Forum!
    Dave
    Raysoncraft 18LP basketcase

  7. #7
    MoJetBoPar
    Thanks DaveA!
    Yeah, A boater buddy once told me that the velvet drive is nothing more than a main planetary gearset or "front clutch pack" of what was previously an automatic trans from a passenger vehicle.
    I do all of my own automotive repair and rebuilds other than A/C and transmissions, but will be taking some classes in that in the next year or so. It's stuff that I wouldn't feel right having someone else do.
    As mentioned above, I'll post an update as to what I find tomorrow and I've got some pic's being developed onto a CD that I'll somehow get posted too.
    Thanks again, Dean

  8. #8
    MoJetBoPar
    Hey guys,
    I just looked at my velvet drive and it doesn't have the gear reduction unit on it. It looks like an aluminum spacer was used to fit another tailshaft on.
    I've got pics of the whole boat and if someone would help me post them, they are on a cd, it would be greatly appreciated.
    Thanks for all the help.

  9. #9
    Stab-n-Steer
    MoJet,
    E-mail them to me and I will post them.
    S&S

  10. #10
    grimreaper
    Do I sense a name change now to MoVeeBoPar ??
    WELL I have a 71 Stevens getting put together JUST furrrr you !!

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