my underwater exhaust extensions

Discussion in 'Inboards' started by sdowney717, Jul 21, 2014.

  1. sdowney717
    Joined: Nov 2010
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    Location: Newport News VA

    sdowney717 Senior Member

    They are made of hard red rubber and I have the wedges for my curved transom glued onto them.

    I looked them up from a patent number and they were in production in the 1960's.
    They certainly have lasted the decades well.
    Opening measures 5.75 inches. These were cut to sit flush to boat bottom. When new, the down leg was maybe 6 inches longer.

    They are unscrewed from hull for some hull work but will go back on. They can grow barnacles on the inside.

    I finally found another example on a 1975 Chris Craft on youtube.
    Anyone ever seen or have these? I have never seen these on any boats.

    These do help with engine fumes.
    [​IMG]

    [​IMG]

    [​IMG]

    They show up at the 47 second area on this video
    And dont seem to restrict his speed.
    https://www.youtube.com/watch?v=6X8bPaIFq1k/
     

    Attached Files:

  2. keysdisease
    Joined: Mar 2006
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    Location: South Florida USA

    keysdisease Senior Member

    Those are vortex generators, they create low pressure that keeps the exhaust gasses underwater a little longer quieting the exhaust. Below is an example of something similar for a larger boat:

    :cool:
     

    Attached Files:

  3. sdowney717
    Joined: Nov 2010
    Posts: 852
    Likes: 32, Points: 28, Legacy Rep: 274
    Location: Newport News VA

    sdowney717 Senior Member

  4. gonzo
    Joined: Aug 2002
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    Location: Milwaukee, WI

    gonzo Senior Member

    They were mainly to keep the noise down at lower speeds.
     

  5. sdowney717
    Joined: Nov 2010
    Posts: 852
    Likes: 32, Points: 28, Legacy Rep: 274
    Location: Newport News VA

    sdowney717 Senior Member

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