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Overheating issue Yamy 115hp 1987 model

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  • Overheating issue Yamy 115hp 1987 model

    I have done what I think is everything to fix this. I have taken off the heads and all cooling jackets drilling out all the blocked holes etc replaced the poppet valve and associated spring etc. Replaced the water pump impeller. Tested the therostats and heat sensors they all seem to be working fine. I have put a hose on the pipe leading from the water pump up to the motor to see if the water goes up freely and dosent blow the hose off which seemed fine. The heat alarm goes off at about 4200 rpm. After cleaning it out the alarm stops alot quicker than it did so there is much more water flow but it (the alarm) still goes off. Any ideas out there would be greatly appreciated.

  • #2
    uptheriverwithoutapaddle, to iboats...

    I am not understand the "drilling out all the blocked holes etc". Exactly what did you drill out? Some times blocked holes are there to channel the water through the head and block in a designed flow to maintain the uniformed temperature across the engine so there no hot spots or too cool spots. So exactly what holes did you drill out? Secondly, how did you check the thermostat and sensor to verify they are good? What method did you use? Post those answers so we can understand your situation better.
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    • #3
      might look up Rydlyme marine scale remover to see if you want to try that


      • #4
        Sign up today
        Sorry for such a late reply. A lot of water has gone under the bridge since then. But to answer you questions. I just drilled out holes that had narrowed with scale I could poke a little bit of wire through so I just cleaned the up. The sensors I checked with a thermometer and heated water using a primus gas burner. When they reached about 90 degrees Celsius they went off ( tested them both separately)
        ​In the end I took the heads off and cleaned everything out. There was some small blockages in the heads. I got it back together went for a burn and the alarms went off at about 4500rpm like I nearly busted my head on the steering wheel when it happened.
        ​But I mechanic told me that there is a little rubber seal in the the lower leg the sits just behind the water pump. ( I had fully replaced the wather pump by this stage even though it looked ok.) But when I replaced this seal along with a little bit of aluminium that is sits with bingo no more alarm. So I think with all the junk I got out if definitely needed a clean as well as the poppet valve needed replacing but this rubber seal was the difficult one. But all good now.
        ​The nutra salt is not worth trying to clean out a clogged motor it does dissolve the crystals to some degree but only good as a rinse aid.