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2859 With Surface Piercing Drive

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    2859 With Surface Piercing Drive

    Earlier today my wife and I were driving from Anacortes to Everett, WA and briefly got behind a 2859 being towed on a trailer. It was unique in that the stern drive had been replaced by a surface piercing drive similar to this one. Unfortunately, the driver got pulled over by a State Patrolman before I could shoot a photo. Are any of you familiar with this boat?
    1999 3788, Cummins 270 "Freedom"
    2013 Boston Whaler 130 SS
    Anacortes, WA

    #2
    Let's try the photo again.... the drive on the 2859 looked like this one:
    1999 3788, Cummins 270 "Freedom"
    2013 Boston Whaler 130 SS
    Anacortes, WA

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      #3
      Wow, that's one LARGE prop!
      2007 Discovery 246
      300mpi BIII
      Welcome island Lake Superior

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        #4
        My guess is she ain't going to be a planing boat anymore
        or maybe so, never seen that before.....
        Dave
        Edmonds, WA
        "THE FIX"
        '93 2556 5.7 Bravo II 2.0:1 18 1/4x19 P
        (.030 over-Vortec top end-part closed cooled)
        The rebuild of my 2556 https://www.baylinerownersclub.org/f...76?view=thread
        Misc. projects thread
        https://www.baylinerownersclub.org/f...56-gctid789773

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          #5
          Well the surface drive boats I've seen go like a bat outta hell but I can't say anything about the particular boat you've seen.

          the surface drive prop only runs half in the water so it can spin up a bigger prop.

          there is a boat on the lake near me that is like the one in this video. Kind of a odd looking thing and it sounds kind of like a 4 stroke lawn mower. Goes in real shallow water.


          https://m.youtube.com/watch?v=fWfNThmE9Kg

          Here.is a good video that kind of explains why to use them. I'm not sure what the benefits would be on a bayliner though.

          https://m.youtube.com/watch?v=zN7TJG-ZAWs


          I never get too much of this video I can watch it a hundred times. Granted not the same type of surface drives but I believe the principle remains the same. In 2 of the videos the entire engine and drive move to be able to steer kinf of like a outboard but with out a lower lower gear box.

          https://m.youtube.com/watch?v=ybpdNcMPs8s



          By the way that is an interesting aft /stern anchor the guy has set up in the picture. I wouldn't want that getting lose with the surface drive spinning.
          1989 Avanti 3450 Sunbridge
          twin 454's
          MV Mar-Y-Sol
          1979 Bayliner Conquest 3150 hardtop ocean express.
          Twin chevy 350's inboard
          Ben- Jamin
          spokane Washington

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            #6
            Surface drives are primarily used on high speed applications like race boats because of lesser drag associated with less gear in the water. About the only advantage on lower speed boats would be shallow water capability.

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            • Nauti_Mike
              Nauti_Mike commented
              Editing a comment
              +1 Unless this guy is forced to run in 2 foot of water there is no advantage of using this setup on this boat. On surface drives half the prop diameter is above the water when running, that would be scary with the prop on the picture but I doubt this setup can achieve that running attitude. .

            #7
            Looks like he’s trying to make up for something......
            P/C Pete
            Edmonds Yacht Club (Commodore 1993)
            1988 3818 "GLAUBEN
            Hino EH700 175 Onan MDKD Genset
            1980 Encounter Sunbridge "Misty Blue" (Sold)
            MMSI 367770440
            1972 Chevrolet Nova Frame off Resto-mod in the garage
            Boating on the Salish Sea since 1948

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              #8
              Actually, surface piercing drives are not just for racing. Here are a couple of good articles on the topic: https://www.powerandmotoryacht.com/boats/arneson-drive, https://www.boatingmag.com/boats/basics-surface-drives
              1999 3788, Cummins 270 "Freedom"
              2013 Boston Whaler 130 SS
              Anacortes, WA

              Comment


                #9
                Site ate the long explanation I typed so here's the short-ish version.

                A regular prop's top speed is limited by cavitation. As the prop spins faster, the water pressure becomes higher behind it, but lower in front of it. Eventually the forward water pressure becomes so low that the front surface of the prop cavitates (the liquid water there converts into a vapor). When that happens, you lose thrust because the prop ends up throwing water vapor behind it instead of liquid water. Newton's 3rd law says the weight of the water thrown back by the prop is what pushes the boat forward. If you replace that water with lightweight vapor, suddenly you lose your thrust and your boat can't go any faster. The cavitation bubble collapsing can also pit or fracture your prop.

                For boats which need to travel at or beyond speeds where this happens, you need what's called a supercavitating prop. Those are designed to continue to push water back even after the propeller begins to cavitate. They are not as efficient at low speeds as regular props though. They're usually surface-piercing because if you're going to cavitate anyway, the depth doesn't matter (positioning the prop deeper increases the ambient water pressure, making it harder to cavitate). Putting it at the surface means you can move some of the support structures out of the water eliminating drag, and the cavitation bubbles draw in air from the surface and thus won't collapse so won't damage the prop.

                Another popular alternative is a waterjet. Those use an impeller instead of a propeller, so can generate higher rearward water pressure (faster speeds) without cavitating. They're quieter and cleaner than surface piercing props (throw water straight back, instead of all over the place). Their drawbacks are that they're not as efficient, and they don't work in reverse. You need a reversing scoop which drops over the outlet and redirects the jet forward. It doesn't redirect it perfectly forward though, and the jets can end up churning the bottom of the harbor, kicking up bottom debris which then gets sucked into the waterjet intake. Waterjets can eject water above the waterline though, which makes them the propulsion of choice for hydrofoils.
                1994 2556, 350 MAG MPI Horizon, Bravo 2

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