Cooling Question

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  • ejay
    Senior Member
    • Jul 2022
    • 68

    Cooling Question

    I saw the announcement about the FWC system from MMI, which got me thinking about my own system. I have an full flow system, but I am puzzled after looking at the diagrams as to how the raw water diverted to the engine block actually cools the block. There must be some sort of a pipe that traverses the block before emptying back into the thermostat, correct? The illustrations and explanations suggest to a novice like me that the raw water is just washing around somewhere inside the engine.

    EJ
    78 Cat 30
    EJ
    78 Catalina 30
  • Dave Neptune
    Afourian MVP, Professor Emeritus
    • Jan 2007
    • 5117

    #2
    No. The coolant flows through the block and out the exit fitting to the HX then back to the pump to repeat the journey collecting the heat out of the engine.

    The raw water is pumped into the HX where it draws the heat out of the "coolant" then exits the HX through the exhaust and also cools the exhaust so the hoses don't melt.

    Two separate systems.

    Dave Neptune

    Comment

    • Al Schober
      Afourian MVP
      • Jul 2009
      • 2034

      #3
      If you have no heat exchanger, they you are raw water cooled with one pump. Outside water goes through the engine, exhaust system, then back to the outside.
      If you have a heat exchanger and two pumps, then you have two systems. First is engine system. Fluid is 50% glycol. Pump to engine to heat exchanger back to engine.
      Second is heat exchanger system. Fluid is sea/lake water. Pump to heat exchanger, exhaust system, then back to sea/lake.

      Comment

      • ejay
        Senior Member
        • Jul 2022
        • 68

        #4
        I don't think I have a HX, at least i have not found one yet. The diagram below represents my system, but I dont really understand how the raw water washes around inside the engine block and then back to the thermostat.
        Attached Files
        EJ
        78 Catalina 30

        Comment

        • Dave Neptune
          Afourian MVP, Professor Emeritus
          • Jan 2007
          • 5117

          #5
          The raw water flows from the pump to the "T" fitting where it is injected into the block when the t-stat is open and blocking the bypass which is only operational when the bypass is closed. When the T-stat is open it directs the water to the manifold and then out the exhaust. This is why the T-stat is a 2 stage because when fully open it blocks the bypass forcing all the water through the block.

          When running without a T-stat as many of us do the temp is controlled by restricting the bypass thus forcing the water into the block to circulate out at the T-stat housing to the manifold and out the exhaust. The temp is controlled by a valve which is adjusted "closed to run cooler" by restricting the bypass and more "open for more heat" allowing more water to bypass the block.

          Either way works well. Hope this helps you to understand the flow of the water.

          Dave Neptune

          Comment

          • ejay
            Senior Member
            • Jul 2022
            • 68

            #6
            This may be a stupid question, but why have a bypass option at all? Why not just push all the water through the block, even when the engine is cold?
            EJ
            78 Catalina 30

            Comment

            • Dave Neptune
              Afourian MVP, Professor Emeritus
              • Jan 2007
              • 5117

              #7
              Since "cold" water is being drawn in all of the time the engine would not warm up. To allow the engine to reach operating temperature varying the amount of water to the block for different conditions is necessary to maintain proper temps. And a good amount of water is needed to keep the exhaust cool thus the bypass in a raw water cooled engine.

              Dave Neptune

              Comment

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