Buy Yamaha Outboard Parts


No announcement yet.

yamaha 9.9hp, possible blockage

  • Filter
  • Time
  • Show
Clear All
new posts

  • yamaha 9.9hp, possible blockage

    tryng to work out if i have a blockage, or is this right.

    in the vid, the lower cylinder is pumping water out however the clear hose belongs to the the upper cylinder is not pumping anything.

    the picture below shows another head the same as mine, but witht the upper cylinder blocked

    vid below

    pic below

  • #2
    it is blocked.
    rather normal.
    most times I can unblock it with air.
    remove the ex cover and start digging and blowing.
    occasionally I have to remove the rocker cover.
    remove the two core plugs and rod the passage out.
    the core plugs are NOT sold by Yamaha.
    to remove them you must destroy them.
    drill a hole in them about 7/32,tap 1/4x20.
    use a threaded rod with a nut and washer to pull them.
    have your local machine shop make you new ones.
    I actually have a few in my box someplace.
    install them with Loctite 518.


    • #3
      compressed air to the blocked outlet, no result , not even a wheeze...
      rod the top plug maybe sounds like a good idea, was thinking of whipping the head off..


      • #4
        All these tubes are outlets. The only inlet is the tube in the leg supplying water to the block and then through the cooling passages into the head. After circulating through the head some goes sideways into the exhaust, some through the thermostat once it is open and the rest through the 2 nipples in the pic. The tube from the thermostat loops round behind the CDI and joins the tubes from the the 2 nipples and on to the telltale. The telltale informs only that the pump is working and that at least one of the cooling passages is not blocked.
        The co!our scheme suggests an old engine, and head removal likely to be needed. Removing the thermostat and/or the exhaust cover plate on the side of the block will give an idea of how much crud there is inside.
        See my posts and advice from others by searching 9.9 cylinder head removal......


        • #5
          Here is the link

          This engine is now running very well indeed.......


          • #6
            Originally posted by cleddau1 View Post
            Here is the link


            This engine is now running very well indeed.......
            Thanks Claddau1 that should help the OP out with his problem.

            Out of curiosity how warm is the water coming out of the telltale on your engine when running at operating temperature?

            Glad to hear your engine is now running good.


            • #7
              I don't think I mentioned removing the head.
              why remove the head????
              I did mention how to fix it.
              yall do as you wish .


              • #8
                Not measured temperature of telltale water but felt lukewarm to tepid; could hold fingers in it indefinitely; engine is now winterised but would be interesting to measure actual temperature when winter is over; currently 2 to 3 Celsius degrees below with freezing rain, hailstorms, sleet and a blizzard forecast.....


                • #9
                  Sounds like nice weather...Thanks for the information...