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Thread: Riser drains

  1. #1
    Join Date
    Aug 2013
    St. Louis

    Default Riser drains

    When I bought my 89 Sunsport a couple years ago, the manifold plugs were pretty corroded and the riser gaskets had a small leak. I ended up replacing the gasket, which involved removing some very rusty unpleasant bolts, retapping the threads, and replacing the plugs with new plugs ( Given the angle of the exhaust coming off the riser, you really can only retap these threads with the riser off.

    Right now I can remove the plugs with a socket wrench without trouble, but I'm not keen to see the threads deteriorate over time and need retapping.

    I'm thinking about replacing the plug with a valve system. Skidim has a stopcock drain ( The guys on the CC pages think this is likely to jam with a little corrosion and recommend using a larger bore drain cock like this: 6D912_AS01.jpg ( ... yes it will need a 3/4" to 1/2" reducer).

    Has anyone had any experience with a manifold drain? Just keep using the new plug and hope for another 20 years on it?

  2. #2
    Join Date
    Oct 2012
    Guelph Ontario


    I can't find any definitive pics of my own boat, but from memory, there may not be enough room to turn that thing once it's installed. It's pretty tight back there, but really, for 20 bucks what do you have to loose?

  3. #3
    Join Date
    Aug 2009
    London, Ontario, Canada


    Why not use a ball valve that you can poke to prevent corrosion blockage
    2009 21v Worlds 340 Cat
    run your engine after you change the oil

  4. #4


    I've had the one like you linked to on Skidim for probably 5 years now, never had a blockage issue. But I also thoroughly flushed out my manifold and risers in the recent past for other reasons, so there's likely less junk floating around in mine than others of a similar age. You could probably spin off the valve from the elbow and get a wire in there to clear it out a bit if you had to. Then you could also take it off completely every few years... better than every year for sure.

    And as was discussed at length this fall, with these drains in particular I still add non-toxic antifreeze to be sure to displace or dilute any water that might be left in the manifold after draining. Removing the whole plug is a much more certain way of getting the water out, but this is a nice quick way and the AF provides another layer of protection.

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