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Water in all cylinders on Merc 5.0 (305)

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  • Water in all cylinders on Merc 5.0 (305)

    I was driving along at about 2000 rpm when the engine started to make a strange sound and the stop completely. When I pulled the plug water come out of all of the cylinders. I cranked the engine over with the plugs out to remove any water but it cranked very slow and seamed to labour. Any suggestions?

  • #2
    Re: Water in all cylinders on Merc 5.0 (305)

    Sounds like your exhaust manifolds may be cracked causing water to leak into your cylinders.Better squirt some mystery oil in each cylinder and turn the engine over by hand about 4 turns.. then pull the manifolds off to take a look for cracks..Just my 2 cents..


    • #3
      Re: Water in all cylinders on Merc 5.0 (305)

      Manifolds won't put water in the cylinders with the engine running. To get water in all the cylinders that fast, the engine may have dieseled and spun backward and sucked the water up the exhaust. Sounds like the engine may have over heated. Remove the Outdrive and be sure its not the problem causing the engine to spin slowly.


      • #4
        Re: Water in all cylinders on Merc 5.0 (305)

        i would be looking at my intake manifold.


        • #5
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          Re: Water in all cylinders on Merc 5.0 (305)

          Actually a leaking exhaust manifold to exhause elbow gasket will put enough water in to a cylinder to shut down the moter. Those moters have overlapping valve systems, the exhaust valve closes after TDC, so it does suck back a little into the cylider. Usually it's cylinders 5-8 that get the water, especially 7 and 8. The exhaust elbow gasket has been an extremely weak point in all mercruiser motors, that is why they have finally gone to dry stack manifolds and elbows, just like the race motors. I think that more than likely it's either a bad gasket, or more likely if you've never had the elbows off, the sealing surfaces between the exhaust elbow and manifold are shot. I see this sort of thing all the time, it happens worse in salt water boats, but is a problem for all mercuisers. Have it checked out, but it may have already done it's damage.ScottI actually pull my elbows every other year, clean the surfaces on both manifold and elbow, inspect for wear and replace with new gaskets. The gaskets are cheap, and the whole process takes about 2 hours. Plus I've peace of mind that I'm not going to injest water, and tuilp a valve, or bend a conrod, or bend a valve. All of which happen during a hydrolock.