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Cylinder head leak 1997 150 hp yamaha

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  • Cylinder head leak 1997 150 hp yamaha

    i bought this motor last week,got a good deal on it,but it needed new cylinder head gaskets i put them in a couple of days ago,and i have a small leak,the leak i am talking about is about 1-2 drops ,I have been watching it ,it's not on the boat yet it's on a motor stand,when i start it about 30 seconds later i get one small drop of water between the head a gasket,then 30 seconds later another drop then it stops,but i have only run the motor for about 3 minutes,i put the gasket on dry,as i was told to do,my questions is do i need to fix this and how ,like a gaskets silicone or something and will i have to buy another gasket thanks

  • #2
    Re: Cylinder head leak 1997 150 hp yamaha

    Did you check the heads for true or at least resurface it with sandpaper on a flat surface?
    I believe they call for a new gasket every time you pull the heads, and I have never tried to reuse one.
    Did you torque the head bolts like the manual says in stages and following the correct pattern?

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    • #3
      Re: Cylinder head leak 1997 150 hp yamaha

      No i did not use sandpaper ,i used a 3M scouring pad yes i did torque to the right spec. 22 lbs and went exactly in the torque sequence" i have the manual" like i said it leaks about 2 drops and i mean a drop, then i stops i have not mounted the motor on the boat yet ,as i am repair the boat and that may be about a month away,I marked it with a magic marker exactly where it is coming out ,my ? is will this get worse? is it ok to live with this,is there a gasket sealer for yamaha gaskets if i decide to buy a new head gasket and should i use it thanks for your quick response.

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      • #4
        Re: Cylinder head leak 1997 150 hp yamaha

        Before taking it all apart and redoing it, and for just a couple of drops, you could run the motor for a while at full operating temperature and then re-torque all the head bolts and see if that does it. If not, then better remove heads and flatten/true them up with the emory cloth on a flat surface. Probably just a bit of warpage between head and block. Good Luck!

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        • #5
          Re: Cylinder head leak 1997 150 hp yamaha

          thanks Robert
          It will be about a couple of weeks before i put the motor on the boat ,i will try your suggestion and post the results on this same thread when i do it thanks for all your help everybody

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          • #6
            Re: Cylinder head leak 1997 150 hp yamaha

            What made you change the head gaskets in the first place?
            Was it a internal leak into the cylinders, between the cylinders, or something else?
            A small leak on the outside is not too bad, but any leak into the internals is real bad. that is why I always resurface or at least check heads before reinstalling, and checking the block would be a good idea also but not always easy.Especially if there was a problem with head gasket to start out with.

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            • #7
              Re: Cylinder head leak 1997 150 hp yamaha

              Well when i bought the motor ,i knew it would be a couple of weeks before i put it on the boat, around the heads where the gasket went there was a lot of salt water build up is the term i guess,and i looked real bad i have the motor on a rack in my garage and my boat is not ready so i decided to change it out,i will be honest the cylinder head did not look good but i was to late i had taken it off already now here is the kicker i have a old 1991 225 yamaha just the blocks i have taken the cylinder heads off and they look greati would like to know if the will fiti looked it up from a yamaha website and the are there part numbers
              My 1997 C150
              cylinder head 6G5-11111-04-94
              head gasket 6G5-11181-A1-00
              1991 225 hp the numbers are real close and i made a couple of
              cylinder head 6R5-11111-01-94 measurements and seem real close thanks
              head gasket 6G5-11181-A0-00

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              • #8
                Re: Cylinder head leak 1997 150 hp yamaha

                How did the anodes look in the block, did you change them out while you had it open?
                Did the passages look bad or was it just the outside that was corroded.

                The heads are different #s and their superseded #s are different also, So I do not think they would be a direct replacement. But maybe someone knows if the will fit and what the differences are.

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                • #9
                  Re: Cylinder head leak 1997 150 hp yamaha

                  The passages looked good and the anodes were so so so i did not change them,i am looking to get 1 or 2 years out of this motor and then buy something newer,in a couple of weeks when i put it on the boat and run it i will bring up this thread agian and let you know how the leak is doing and where to go from there thanks everone for your help

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                  • #10
                    Re: Cylinder head leak 1997 150 hp yamaha

                    Originally posted by robert graham View Post
                    Before taking it all apart and redoing it, and for just a couple of drops, you could run the motor for a while at full operating temperature and then re-torque all the head bolts and see if that does it. If not, then better remove heads and flatten/true them up with the emory cloth on a flat surface. Probably just a bit of warpage between head and block. Good Luck!
                    at this point I would try this, ideally you should have had the head decked by a machine shop.
                    Love the life you live, live the life you love-Bob Marley

                    sigpic

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                    • #11
                      Re: Cylinder head leak 1997 150 hp yamaha

                      Thanks Capt Sam
                      How will i know how much of the head to take off?or will they know how much to shave down ? thanks

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                      • #12
                        Re: Cylinder head leak 1997 150 hp yamaha

                        Just enough to get it back to flat.
                        Even the Yamaha manual says to use 400-600 grit wet sandpaper on a flat surface like a thick pane of glass, moving in a figure 8 motion and rotating from time to time to make sure you do not remove too much from any one place.

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                        • #13
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                          Re: Cylinder head leak 1997 150 hp yamaha

                          Thanks 99YAM
                          i will post when i get the motor on the boat and go from there

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