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  • Motor work

    The ole trusty '92 Johnny 225 finally broke......the magnets in the flywheel came loose, my wrench fixed them (garanteed) his work and did something else for me, he drilled the vent holes in my prop.......what a difference !! She jumps on plane now !!

    She never sounded so good.

  • #2
    Houw about some pix of the prop with the vent holes drilled. Is there a science to it or...

    Interesting..

    Bob
    Bob Carpenter [br] Maine[br]1969 Boston Whaler 13\' (Annie3 1/2) [br]Built Annie2 and Annie3 which can be seen in The Project pages[br]

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    • #3
      Kinda hard to describe the holes. They are 3/8 inch holes (can be much bigger....depending on application) drilled 1/2 inch from the back of the hub and 1/2 inch from the edge of the blade... for 3 blades you would have 3 holes, 4 blades 4 holes. A lot of new props are vented, getting a look at one will help visualize this.

      The way it was explained to me is: the holes allow some of the exhaust gasses to escape during acceration causing cavitation, allowing the engine to "wind up faster" as engine winds up the exhaust by-passes the holes so they never interfer with blade performance at speed. It allows the engine to get into it's power band quicker..........it works, like a shot of adrenaline !!

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      • #4
        This "shot of adrenaline" is actually the development of horse-power which is work over distance over time. Obviously that translates to RPM's. You can't have horsepower without RPM's. This is due to the fact that the lower the RPM's the fewer explosions per second you have which is where your power comes from.

        The water being sucked across the blades of the prop will eventually overwhelm the exhaust (which wants to travel straight anyway) and become thrust. But since you now have momentum on the prop and more explosions per second, you have POWER!

        I hope this helps.

        -Pat.
        18ft MonArk tri-hull: 140HP Mercruiser Alpha One - still in pieces...to be continued[br](I know it\'s not a Mako, but hey, its mine!)[br] Time\'s fun when you\'re having flies![br]president/hostmaster:[br]P.Ring Technologies[br]Cornerstone IT, LLC[br]LOUISIANA WEB HOST, LLC.[br]CompTIA Certified Professional A+/Network+ // Microsoft Registered Partner

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        • #5
          Hmmm...is this something worth doing to my aluminum prop? Or is it only required in certain circumstances?
          ROGUE I[br]1978 235 CC[br]Newburyport, MA[br]ROGUE II[br]1987 17\' Montauk[br]Camden, ME[br]

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          • #6
            quote:


            Originally posted by Cyclops


            This "shot of adrenaline" is actually the development of horse-power which is work over distance over time. Obviously that translates to RPM's. You can't have horsepower without RPM's. This is due to the fact that the lower the RPM's the fewer explosions per second you have which is where your power comes from.


            The water being sucked across the blades of the prop will eventually overwhelm the exhaust (which wants to travel straight anyway) and become thrust. But since you now have momentum on the prop and more explosions per second, you have POWER!

            I hope this helps.

            -Pat.


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            • #7
              some props even have multiple vent holes and come with plugs so you can fine tune it to your liking
              1990 261 T/2001 200 HPDIs[br]Basking Ridge/Mantoloking NJ[br]

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