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Thread: Propellor Slip

  1. #16
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    I don't know about alpha drives but that is the biggest water intake I have ever seen and was probably designed for a non planing hull. 4" x 6" x (2"?) is enormous, my Blackhawk drive intake on the skeg was a slot about 2" x 1/2" and that cooled a 540ci motor. For that thing to deflect water 5" over a 2+' distance seems like a certainty to me.
    1978 Magnum Starfire "MAYHEM"
    1994 Donzi 22 Classic 540/Blackhawk - Sold
    1982 Midnight Express 32 SS

  2. #17
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    That pickup on the bottom = not good

    I had a 1987 20' Minx with stock 350mag/270HP and Alpha. At WOT 4600rpm, spinning a 23p Mirage and 60 to 63mph depending on the load. Did some engine upgrades including a Tempest cam and gained 200-300rpm and 2-3mph on top.

    Your boat should be running faster and that prop not blowing out...
    Thank you, Patrick
    1994 18' Classic 350Mag Alpha

    Previously owned Donzis -
    1996 22' Classic, 502Mag Bravo
    1987 20' Minx, 350Mag Alpha
    1975 18' Classic, 350Chevy Volvo 280

  3. #18
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    Drive height

    How do I best verify the height of the drive? I cannot trim it down all of the way while on the trailer. Can anyone give me the dimension from the centerline of the bottom bolts on the transom assembly to the keel?

  4. #19
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    rough numbers

    X dimension is from drive shaft centerline to the bottom of the hull and most V bottom boats are set between 17" and 18".
    I believe an Alpha drive is about 22" from prop shaft to drive shaft which would put the prop in the neighborhood of 5-1/2" below the bottom.
    Thank you, Patrick
    1994 18' Classic 350Mag Alpha

    Previously owned Donzis -
    1996 22' Classic, 502Mag Bravo
    1987 20' Minx, 350Mag Alpha
    1975 18' Classic, 350Chevy Volvo 280

  5. #20
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    Check the trailing edge of the lower unit hub . Any raised bur on the hub will cavitate the prop. Check the prop thrust washer and make sure the taper is not worn and rubbing the prop on the lower's hub and the washer on the bearing cap.
    machinist ,bore it deeper,ream it bigger, and lap it to a fine finish



    https://www.facebook.com/photo.php?v...=2&theater

  6. #21
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    Oct 2001
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    Update

    No apparent turbulelence coming from water intake.
    Watching the water coming off of drive and prop it does not appear to be slipping at the prop.
    It does feel more like the coupler.
    After several runs messing with the trim and watching the water coming off of the transom, I accelerated to approximately 4000 rpm with the drive trimmed all of the wY down and could feel slipping, a couple of hours later, while heading back to launch ramp, there was no apparent slipping
    Pulled the drive, no apparent wear on the drive shaft or in the female spline inside the coupler.

    Going to just get the coupler changed ang eliminate it as a potential problem.

  7. #22
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    If the coupler was bad you would have a definite burning rubber smell from inside the engine compartment

  8. #23
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    Quote Originally Posted by Ralph Savarese View Post
    If the coupler was bad you would have a definite burning rubber smell from inside the engine compartment
    Not always, but usually.
    I just changed one on the TR that didn't smell, no smoke, and physically looked fine when I removed it.
    A suggestion on the Minx, after loosing a coupler on my Minx, I chose to replace the Alpha coupler w/a
    Bravo coupler as they are significantly stronger. You may have to replace the flywheel cover w/one w/a larger center hole for clearance.
    George Carter
    Central Florida
    gcarter763@aol.com
    http://kineticocentralfl.com/


    “If you have to argue your science by using fraud, your science is not valid"
    Professor Ian Plimer, Adilaide and Melbourne Universities

  9. #24
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    Oct 2001
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    Waiting to get it back from mechanic. I have been out of town a lot and no time to work on it. I had someone pull engine. He said that the coupler appears to be bad. I have not had a chance to see it. Things will slow down with travel in a couple of weeks, should have it back together by then. Will update with the results.

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