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Overheating 350 MIE

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  • Overheating 350 MIE

    I just drained and replaced my coolant in my 236 mako. I am wondering if I screwed up or if my waterpump (freshwater) bad. I put new coolant in ran it with the cap off, let it come up to temp and burp a bit. Put the cap on and the thing is not getting coolant past the thermostat. So I don't think my water pump is pumping water. Did I miss something? Could it have that big of an air pocket so that no coolant at all is getting past the thermostat?

    Any suggestions.

    andy

    One more thing, I though the exchanger was getting a bit warm last time I ran it, the engine didn't get that hot but I didn't let it run that long. The coolant side of the heat exchanger was really warm.
    Andy

  • #2
    Hi Andy, the best way to check is is to pull the hose off the outlet side of the pump and see if its pushing water. If its on a trailer and you are running a flush kit on your engine make sure your sea cock is closed or you may not draw water to the pump.

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    • #3
      Gary,

      Its freshwater cooled and has great pressure coming from the raw water pump, with plenty of water coming out of the exaust.

      These engines have a side port that lets coolant through at all times. More just get through when the thermostat is open. I'll run it with the output hose off tomorrow to check, but the hoses are dry.

      andy
      Andy

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      • #4
        Did you change the thermostat when you did this work?? It could be a bad thermostat from the factory. I saw one many years ago and now every time I change one on a boat OR a car/truck I ALWAYS check their operation by placeing them in a pan of water on the stove. It takes a little longer but it's time well spent if it's bad. The thermostat should open up all the way in the pan of boiling water and if removed, close down within a 30 seconds or so. If it dosent get another because it's not working properly.

        Mike
        1973 22 CC Milford, CT USA[br]

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        • #5
          Do you remember how much coolant you took out of the engine? Did you put the same amount back in? You could have an airpocket in the system somewhere. Bleeding a coolant system isn't as easy as just running the engine w/ the cap off. Just a guess, but the exchanger is the highest point on your engine? your air pocket could be in there?
          [br]Michael R. Delgado[br]1972 Mako 22[br]http://classicmako.com/forum/topic.asp?TOPIC_ID=15745[br]1976 Mako 25[br]http://classicmako.com/forum/topic.asp?TOPIC_ID=18013&SearchTerms=mako,25[br]

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          • #6
            I HAD A 470 MERCRUSIER ONCE AND THE HEAT EXCHANGER STOPPED UP. I TOOK IT APART AND CLEANED THE CALCIUM OUT BY DROPING COILS IN MURATIC ACID WITCH I HAD POURED IN ONE OF MY REAR LIFT OUT PLASTIC STORAGE BOXES. BE VERY CAREFUL WEAR GLOVES. I DID IT OUTSIDE WORE GLOVES AND HELD MY BREATH WILE I EASED IT IN. THEN RAN LIKE HELL. I DON'T KNOW HOW I GOT TO BE 54 YRS OLD! ALSO CHECK THE ELBOWS AND MANIFOLDS FOR BEING PLUGGED. SOME MANIFOLDS ARE FWC AND SOME ARE NOT. IT TAKES A HUGE HEAT EXCHANGER TO FWC THE MANIFOLDS.
            OVER BUDGET[br]PEARLAND TX

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