Need Help! Temp alarm going off.

Doc of the Bay · 04-02-2006, 08:46 PM

Need help guys, My temp alarm is going off on one of my 1996 Yamaha 150's when cruising at about 3500 to 4500 rpms, the indicator arrow blinks over the temp symbol on my Yamaha tach in the lower left corner, but, the temp gauge is showing normal, and the water pressure gauges is showing 20-25 psi. When I stop and turn the motor off, wait about 15 to 20 seconds, and restart, it has stopped. I feel I should change the temp sensor, and the thermostat. Where are they both located, and what is you opinion on this. Thanks in advance, Doc of the Bay

bigdawg · 04-02-2006, 10:38 PM

Hi Doc,

I am having the same problem with my 2000 OX 66 200's I have changed water pumps, thermostats and the pressure valve to no avail. I had a mechanic test drive the baot and he suggesting some sort of obstruction behind some plate on the engine. I will let ou know what we find..

Doc of the Bay · 04-02-2006, 10:54 PM

Thanks, keep me updated. Doc

jethro1 · 04-03-2006, 10:01 AM

You need to determine if you have an actual overheat problem or just an instrument indication problem. Don't be in a rush to throw parts and money at the problem. Been there and done that!

If you have good water pressure and, more importantly, the temperature gauge is indicating a normal temperature, it would appear to be a problem with the other gauge. This assumes you have a standalone temp gauge and it is not interfaced or otherwise connected to the overheat indicator on the tachometer gauge. It might even be a one-time fault since you say it has gone away now that you have turned off and restarted the engine.

In any event, thermostats usually control water flow at low (idle or so) RPM. The poppet valve controls flow at high RPM. Since your problem occurred at high power it does not appear to be a thermostat related problem. Best thing I can suggest is to buy a Yamaha service manual from SIM and see what it has to say. It will also give you the location of all of the sensors and stuff.

Salt Shaker · 04-03-2006, 10:27 AM

I have a 2001 150 2 stroke and the temp light blinks when slow trolling at 700 RPM's but no alarm buzzer. Can go to neutral and idle engine up to 1200 give or take and blinking light will go out. Have to do this several times during the day. No problems other than idle. Should my alam be going off if light is blinking?