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Yamaha 20hp, water in one cylinder

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  • Yamaha 20hp, water in one cylinder

    Im having problem with my 20hp 1981 again.. Now it is taking in water in the lower cylinder. I also did a compression test, the upper cylinder has 100psi and the lower 79 psi.

    This sounds to me like the headgasket is broken. But the first thing i'm gonna do is to remove the powerhead, so I have good access to all the bolts to the head. I have tried this before but i'm not sure which bolts to remove?

  • #2
    no need to remove the powerhead just the cyl head bolts.

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    • #3
      Originally posted by rodbolt17 View Post
      no need to remove the powerhead just the cyl head bolts.
      I know, But I wont have enough room for my torque wrench when Im going to torque down the head bolts. It's almost to tight for a normal wrench on the lower bolts on the head.

      I think I found the right bolts to the powerhead atleast, gonna try to remove it tomorrow.

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      • #4
        Ok, I will put together my engine this weekend. But I need to know the right torque for the six bolts for the powerhead. What should I torque them down to?

        The torque for the head bolts is written on the head itself, 2.8kgm.

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        • #5

          Originally posted by luddovitch View Post
          Ok, I will put together my engine this weekend. But I need to know the right torque for the six bolts for the powerhead. What should I torque them down to?

          The torque for the head bolts is written on the head itself, 2.8kgm.
          If it's just the bolts that hold the Power head to the body of the motor than just tighten them up good and snug...no need for torque wrenches there.

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          • #6
            Originally posted by panasonic View Post



            If it's just the bolts that hold the Power head to the body of the motor than just tighten them up good and snug...no need for torque wrenches there.
            Ok, just as I thought, thanks.

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            • #7
              Ok, now I have good compression on both cylinders and the engine is running.

              But I think there is something wrong with the gears. In neutral I can hear a knocking noise and I can feel the gears scraping against eachother when I put my hand on the gear shifter. It feels the same when its in reverse, but there is no scraping in forward.

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              • #8
                Originally posted by luddovitch View Post
                Ok, now I have good compression on both cylinders and the engine is running.

                But I think there is something wrong with the gears. In neutral I can hear a knocking noise and I can feel the gears scraping against eachother when I put my hand on the gear shifter. It feels the same when its in reverse, but there is no scraping in forward.
                Gear shift linkage isn't adjusted right.

                You had Lower unit removed? Or did you just disconnect the shift linkage when you took the powerhead off the engine?

                Need more information, unable to see parts breakdown of that engine online.

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                • #9
                  Originally posted by panasonic View Post
                  Gear shift linkage isn't adjusted right.

                  You had Lower unit removed? Or did you just disconnect the shift linkage when you took the powerhead off the engine?

                  Need more information, unable to see parts breakdown of that engine online.
                  Yes I had lower unit removed. I have removed it many times before but now I must have done something wrong.. I tried to adjust the nuts on the shift linkage but no success.

                  I have found parts breakdown of the engine but from a 1985 (6A9, 20C) model, seems to be the same.

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                  • #10
                    Originally posted by luddovitch View Post
                    Yes I had lower unit removed. I have removed it many times before but now I must have done something wrong.. I tried to adjust the nuts on the shift linkage but no success.

                    I have found parts breakdown of the engine but from a 1985 (6A9, 20C) model, seems to be the same.
                    Where did you find the parts breakdown? I looked on Yamaha Canada and Yamaha USA and cant find it.

                    I think the shifter needs to be in reverse and the lower unit in reverse when you reassemble. Could be wrong on that.

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                    • #11
                      Found the parts breakdown here: http://www.yamaha-motor.eu/uk/servic...-uk/index.aspx Scroll down to Yamaha online parts catalogue


                      Having the shifter in reverse makes sense.. I had in neutral now I think.
                      Last edited by luddovitch; 04-24-2017, 12:43 PM.

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                      • #12
                        Pretty sure Lower unit must be in reverse and shift handle in reverse as well. Then attach shift rod with the barrel nut...try that.

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                        • #13
                          Ok, I attached the shift rod again with everything in reverse and it works now, thanks for the help.

                          But when I was going to start the engine today it was completely dead. I checked for spark with a spark tester, nothing on both plugs. So I checked for bad connection, disconnected the kill switch and with some other plugs, and all of a sudden I had spark again.

                          I figured out that when I am testing for spark, with the spark tester or with the plug, the other plug also must be grounded to the block, otherwise I wont be getting any spark. I find this very strange, I dont think it has always been like this. The engine then fired up, but I wonder why it didn't started at first?

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                          • #14
                            some motors fire both plugs at the same time, so require both plus to be grounded to have spark to travel properly.
                            Have no idea why it did not fire up at 1st

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                            • #15
                              Originally posted by 99yam40 View Post
                              some motors fire both plugs at the same time, so require both plus to be grounded to have spark to travel properly.
                              Have no idea why it did not fire up at 1st
                              Ok, thanks.

                              Now it is only thing left to fix..Its really hard to start when cold, sometimes nearly impossible. I always need full throttle and full choke for it to start after many attempts. Its easy to start right after it has been running but if I leave it for a few minutes it need full choke and throttle again and many attempts.

                              I've noticed some fuel coming out from the carburetor were the air box is located. Bad reed valves maybe?
                              Last edited by luddovitch; 05-14-2017, 08:38 AM.

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