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Thread: 40hp mercury

  1. #1

    Default 40hp mercury

    Installed new water pump now water coming out of spark plugs. Any idea why?

  2. #2

    Default Re: 40hp mercury

    Quote Originally Posted by kimcrwbr1 View Post
    Probably just a water jacket cover gasket. Mercs dont have a head just take the cover off and get a new gasket clean all the surfaces good and use a light coat of aviation permatex on both sides of the gasket. Thats the brown stuff you brush on get the bolts good and snug and let it sit overnight then you should be set to go.
    Depending on your HP and serial number it should look similar to this it`s just leaking out the water jacket cover around the spark plugs. Real common. Be real careful loosening the bolts heating it up around the bolts prior to loosening helps. The bolts tend to break real easy the older the motor. Take your time!
    took water jacket plate off have a small hole in cylinder wall above top spark plug looks to be old but not sure if the motor is toast looks small enough to patch and what should be used

  3. #3

    Default Re: 40hp mercury

    ???... Unusual. Do you know the history of this motor? Pics would be very helpful.

  4. #4
    Join Date
    Sep 2003
    New Tripoli, PA, USA!

    Default Re: 40hp mercury

    Seen that many times, caused be overheating due to a bad impeller.

    The cover has to come off. The bolts will most likely snap off if you simply unscrew them, so you'll need an acetyylene torch to heat the nuts red hot BEFORE trying to remove them. With the cover off, you should flat plate sand it flat, then install a new gasket with lots of silicone. And use all new grade 8 bolts!


  5. #5

    Default Re: 40hp mercury

    Jeff, he says the water cover is off. What about the hole?

  6. #6

    Default Re: 40hp mercury

    Would still like to see the hole. Why and how did it get there?

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