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Mercruiser 3.0 - Leaking cooling water with significant pressure

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  • Mercruiser 3.0 - Leaking cooling water with significant pressure

    Engine Information:
    - 2005 Mercruiser 3.0L, 135 hp, Alpha 1 drive, SN# OW304..., raw water cooling system

    I just purchased the boat and was testing in my driveway with muffs on today and noticed small amounts of water leaking from the front of the engine near the top. I believe this is the thermostat or it's housing? There are 3 pipes entering/leaving the housing as well as 3 electrical entry/exit points.

    The leak was coming from (front view from in the boat looking aft at the block) a small crack near the bolt holding the housing on the bottom left of the housing. If it helps there is an engine lifting hook on the top of this housing. When under load in the lake, it produced a huge volume of water (warm, not hot) that came out from under the engine cover.

    If it helps I can add a picture in the morning of the part and location.

    I appreciate input on next steps, likely other things this could be symptom of and if this something someone with limited engine experience but good handyman skills can replace or if I should take it to a dealer. Also, is this a standard part that I can buy from an auto parts store or is this a marine specific part?

    Thank you - Mike (unhappy first day out with my new boat )


  • #2
    Re: Mercruiser 3.0 - Leaking cooling water with significant pressure

    Simple fix...your thermostat housing has been cracked, probably from someone using too much 'umph' when they inspected and/or changed the thermostat.

    Run...don't walk...to your closest Mercrusier dealer and get a new housing. This is not a part that you can get from Peppy Boys! Be sure that you get a new gasket....

    Happy boating!

    Comment



    • #3
      Re: Mercruiser 3.0 - Leaking cooling water with significant pressure

      Rocky

      Thank you very much. Being a bit new to this, may I clarify that all the other components (except top and back gaskets?) are reusable?

      Cheers,
      Mike

      Comment



      • #4
        Re: Mercruiser 3.0 - Leaking cooling water with significant pressure

        Originally posted by Mikejr View Post
        Rocky

        Thank you very much. Being a bit new to this, may I clarify that all the other components (except top and back gaskets?) are reusable?

        Cheers,
        Mike
        Nothing else should be affected by this. Thermostats are pretty resilient, and are usually replaced needlessly. Nothing that you described suggests that you need anything but a new housing, and gasket.

        If this were mine, I would look up the correct torque value for the bolts and use a torque wrench when I change it out. I am a firm believer in doing this for every aspect of my marine engine.

        Happy boating!

        Comment



        • #5
          Re: Mercruiser 3.0 - Leaking cooling water with significant pressure

          Rocky,

          I picked up my part from a Vancouver dealer while there for work this week and got into the engine last night. As we started to dry fit the parts, the threaded hole for the top of the housing was not manufactured properly and wouldn't accept the bolt. So much for the quality factory OEM parts!

          So another trip to a parts store for a tap and problem solved. I test ran it today and everything looks good!

          Off to the lake tomorrow to test it for real.

          Thank you very much,
          Mike

          Comment



          • #6
            Sign up today
            Re: Mercruiser 3.0 - Leaking cooling water with significant pressure

            Originally posted by Mikejr View Post
            Rocky,

            I picked up my part from a Vancouver dealer while there for work this week and got into the engine last night. As we started to dry fit the parts, the threaded hole for the top of the housing was not manufactured properly and wouldn't accept the bolt. So much for the quality factory OEM parts!

            So another trip to a parts store for a tap and problem solved. I test ran it today and everything looks good!

            Off to the lake tomorrow to test it for real.

            Thank you very much,
            Mike
            Nice work Mike!

            I'm a 'sucker' for happy endings....

            Good luck on your test run...and, Happy boating!

            Comment


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