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Coolant change on closed system Mercruiser advice?-gctid340236

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    Coolant change on closed system Mercruiser advice?-gctid340236

    I want to change the coolant in my Mercruiser 5.0 Alpa 1 Gen 2 closed system. I have never done it and it most likely should have have been done before now. Is there an existing thread on this? I have looked and only found Hino ones, nothing for Mercruiser. Any advice or a link would be appreciated.

    Cheers and Happy New Year
    1979 32 Uniflite Sport Sedan twin 270 crusaders
    2003 Bayliner 2152 210 Classic 5.0 mercruiser - sold
    I wish I knew now what I didn't know then

    #2
    It should be pretty simple. Pull a low water jacket drain plug, or a low coolant hose to drain the coolant, and then reinstall the hose or plug. Then put a mix of 50/50 antifreeze to water in the top filler cap. If you can put a bucket under the plug or drain plug to catch the old coolant that would make the cleanup easier.

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      #3
      E/G = ethylene glycol

      H/E = heat exchanger

      Assuming this is a Half System (engine only):

      To fully drain the old E/G from a 5.0L Merc, you must remove the side engine block drain plugs.

      Then remove the circulating pump suction hose and empty into a container.

      Have the H/E cap open while doing this.

      NOTE: The H/E's pencil anode port is not a drain for the E/G side.

      The circ pump hose should take care of the E/G side of the H/E.

      When re-filling, make sure that your thermostat has the air bleed hole in it.

      Best to use distilled water with your E/G.

      When fire up for the first time, do as you would with a car/truck.... give time for a bit of heat to just open the stat, shut her down.

      Check coolant level... top off... repeat.

      One or two Warm/Cold cycles.... and the air should be purged...... and you should be OK.

      If you have a WH or Cabin Heater, extra measures are required.

      You may also want to have the PH balance tested before you disgard the old E/G and get an idea of what's been going on inside the cooling system.
      Rick E. Gresham, Oregon
      2850 Bounty Sedan Flybridge model
      Twin 280 HP 5.7's w/ Closed Cooling
      Volvo Penta DuoProp Drives
      Kohler 4 CZ Gen Set

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        #4
        This was exactly what I was looking for, thank you.
        1979 32 Uniflite Sport Sedan twin 270 crusaders
        2003 Bayliner 2152 210 Classic 5.0 mercruiser - sold
        I wish I knew now what I didn't know then

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