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I have a 1990 Yamaha 90 HP and the temp light is now going on regularly, want to check the thermostat but cannot find it. Is there a good schematic out there that can show me, or a pic if available. thanks.
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Remove upper cowl, and looking at the back of the motor the thermostat is at the top/back of cylinder head under a square cover with 4-10MM hex bolts.... -
Remove upper cowl, and looking at the back of the motor the thermostat is at the top/back of cylinder head under a square cover with 4-10MM hex bolts....Go easy on those bolts so as not to break them off if the threads may have corrosion on them....you may probably need a new gasket for that cover...Comment
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Thanks Robert, very helpful, the bolts came out really easy. I put the thermo in boiling water and it did not change, so I assume it is stuck? Going to contact my local dealer for new thermostat and gasket. Any other advice/suggestions are welcomed.Comment
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There should be movement of the thermostat when put in boiling water...so it's either stuck or faulty. There may also be a pressure control valve/spring/grommet under that cover...but I'm not certain your model has those pieces....if so, then just clean and replace themComment
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Thanks again, I ordered the gasket and thermostat, let's see what happens when it comes in and install itComment
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So I installed a new thermostat and gasket and it ran without the alarm for a good long ride, next day the alarm came right back on. For some reason I think it may have something to do with the trim of the engine, possible air to water intake - although water comes out of the pisser hose just fine.
What should I try next?Comment
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I would inspect/possibly replace your water pump....Comment
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Ok anything in particular, possibly a link to a diagram or video, thanksComment
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