2000 V150TLRY alarm overheat sensor?

[imported_barlow46]

History: alarm sounds after 5 minutes at 4000 rpm. rpm's drop to 2500 or so. Bring engine back to idle speed and alarm stops after 3 min. So far, I have put in a new water pump impeller, checked t-stats in pan of hot water (both opened at 160 - 170 degrees) Re-installed t-stats. Still have the alarm/horn. Do not have Yamaha gauges (teleflex, I think, on a hurricane deck boat...will be getting yamaha tach, etc. soon.) Took for another test ride and used an IR gun when alarm went off. Starboard head temps around 145 - 155. Port heads around 115 - 135. Engine must be above 3000 rpm to get alarm to sound. Am looking at thermosensor assembly and thermoswitch assembly's. Water pump impeller was installed by Yamaha dealer and watertested. Engine was not run for 3 months after test but alarm went off first time out. Engine does not smoke or feel exceptionally hot when alarm goes off, that is why I suspect sensors. Any help would be appreciated as I don't need another $300 plus bill from dealer at this time.

 

[rodbolt]

Re: 2000 V150TLRY alarm overheat sensor?

are you sure its not an oil alarm ?
t-stat opening temp is 118*-126*F, overheat switch on temp is183-194*F and off temp is 140-165*F.
if its a low oil level alarm it may be a slow transfer,check oil flow.
to test turn the key on,remove the water trap from the engine oil tank,insure the remote is at least half full, drain the engine tank until the horn sounds, when the horn sounds put the trap back in place. the engine tank should refill and transfer shut off in less than 180 seconds.
the trap should be checked for water at least monthly and tested every 100 hours or at least yearly.
quite often a low oil level is due to the oil is consumed faster than the tank can be refilled due to a pinched transfer line,low pump voltage or a clogged remote oil tank filter.
each head has a temp switch, they can be tested with hot water a candy thermometer and a multimeter.

 

[imported_barlow46]

Re: 2000 V150TLRY alarm overheat sensor?

Ok, i could be looking in the wrong place after all. I did use a candy thermometer to check the tstats and I thought I was reading 160 plus before they opened but I could be wrong with these old eyes. I will test the oil flow next. I did remove the oil trip on the engine tank and drain some oil to make sure there was no water in it. None seen. I thought that if I had an oil flow problem, I would have to turn the key off and then on again to reset for the oil problem. I thought the temp alarm would reset without turning the key to the off position and then to on position again. I'll post what I find next. I haven't looked at the remote tank at all but the engine tank has been just below the top fill line. Thanks for the response.

 

[imported_barlow46]

Re: 2000 V150TLRY alarm overheat sensor? UPDATE!

Re: 2000 V150TLRY alarm overheat sensor? UPDATE!

Update & Feedback:

Thanks Rodbolt, I removed and cleaned the remote tank, installed a new tank filter, drained and cleaned the engine oil tank. Put new oil in and bled the system. Took it for a test run (30 min. at all RPM's (1500 - 5500) and no alarms sounded. Looks like I did have an oil transfer problem. Am posting this feedback for others who may have the same symptoms. Thanks again for your help.