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1993 Yamaha 85hp

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  • 1993 Yamaha 85hp

    Cooling problem. New water pump impeller has been installed. The old impeller only had one paddle out of the six. Found no debris when installing new impeller. Have removed thermostat and cylinder head, still found no debris. Restricted water flow from pea hole (hose is clear) and motor runs hot at higher RPMs.Any suggestions on where the blockage could be located or what to do next?

  • #2
    kurtm,
    Those other five paddles, or their remains, have got to be in the cooling system somewhere .
    I'm gonna guess, but you will probably have to remove the upper casing and disconnect the water pump tube that leads from the water pump to the cylinder assembly water jacket - those pieces must be in the tube or in the cylinder/head water jackets.
    Hopefully someone with some experience with this will chime in here.
    Good luck [img]smile.gif[/img] ,
    Ken K

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    • #3
      You didn't mention anything about the pressure relief valve when you said you pulled the thermostat out. The PRV is co-located under the thermostat housing cover, in the hole below the thermostat. Pull that cover off and underneath it you'll find the thermostat in the top hole and a stainless spring and plastic PRV valve in the lower hole. Make sure the PRV passage is clear of debris and there's no heavy mineral buildup under the rubber seat seal of the PRV. Make sure there is nothing stuck in the PRV and that it can close up tight against it's seal.
      But like Ken said, that rubber impeller debris has to be somewhere. Could be stuck in the feed pipe from the waterpump up to the powerhead or something. Run a steel rod up that pipe and make sure there's nothing blocking flow.
      I'll send you a service manual for it.


      Mike

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