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I HAVE A 60Hp YAMAHA 3 CYLINDER. IT STARTS EASILY AND IDLES FINE. THE WATER PUMPS STRONGLY BUT AFTER A MINUTE OR SO THE HEAT BUZZER ACTIVATES. FOR THE FIRST MINUTE IT RUNS SMOOTHLY AFTERWICH IT VIBRATES AND STUTTERS SLIGHTLY AS SOON AS BUZZER STARTS. THIS HAPPENED AT SEA ON MY FIRST OUTING.THE SECOND MOTOR RUNS FINE.IT NEEDS TO BE SAID THE MOTORS WAS NOT USED FOR MORE THAN A YEAR. ONE OPINION I GOT WAS THAT THE THERMOSTAT COULD BE FAULTY DUE TO THE FACT THAT IT STOOD FOR SO LONG.
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Gerrie,
Since the outboard is only a year old, I would not suspect a weak water pump.
The thermostat could be stuck, or faulty, and not opening up all the way - it should start to open at approx 125 degrees f. and be fully open at approx 140. It is fairly easy to remove and test in a pan of heated water with a thermometer. It should open fully at about .120 inches (3 mm).
The thermo switch is designed to close at around 180 degrees f. When this overheat condition is detected, the ignition control goes into rpm reduction mode - the motor will miss and shake pretty bad, and the alarm sounds.
I have personally experienced a faulty thermo switch that prematurely closed at 130 f. and put my C115 into rpm reduction. The thermo switch can be removed and tested also in a pan of heated water also. Monitor the leads with an ohm meter to detect closure - should close at 180 and re-open at 160.
The Yamaha shop manual describes the above procedures - I recommend you get one if you are going to do your own maintenance.
Good luck [img]smile.gif[/img] ,
Ken K -
The 60 and 70 Hp engines have a high volumn low pressure cooling system( thats why water pressure gauges dont work well on these engine's) Since you have 2 engines, remove the other thermostat as well, start engines with thermostats out and compare the volumn of water they do have to have a lot of water to keep cool.Just don't run it no more than have to with thermostat's out.Comment
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