YamahaOX66250 Overheat alarm & increase in RPM

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imported_Jimbob

Recruit
Joined
Mar 24, 2007
Messages
3
Running at 3600 Port engine increased to 4100 w/o moving throttle. Shortly thereafter overheat alarm. Engine would not come off alarm for about 30 min. Had replaced thermostat and water pump about 40 hours prior. Ehgine was peeing prior to alarm. After restart engine ran fine. This is 2d time this occurred. Techs unable to find cause.
Help appreciated.
 
Y

yamamarinetech40

Petty Officer 1st Class
Joined
Dec 17, 2006
Messages
328
Re: YamahaOX66250 Overheat alarm & increase in RPM

You said this was the second time this occured? Back to back or over how long a period of running? Last time same in all ways, like RPM? Did you feel the heads to confirm overheat was real? Did you go into RPM reduction or have you at any time?
 
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imported_Jimbob

Recruit
Joined
Mar 24, 2007
Messages
3
Re: YamahaOX66250 Overheat alarm & increase in RPM

Occurred about 40 running hours apart. After first boat went in for thermostat and water pump replacement. Second was about 40 hours after water pump and thermostat replaced. Both times when the alarm sounded I shut down both engines immediately. Restarted starboard and proceeded on one. Did not feel engine. First time disconnected the flush line and connected my sea water washdown to flush and cool engine. Water discharge was at sea temperature. Engine would not start and alarm persisted. Both times it took about 30 minutes to restart and engine ran fine after restart. The other common condition between the two incidents was a 2-3 foot beam sea on starboard side. Engine was fully down and was not cavitating running through the swells.
 
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