Alarm buzzer - Temp Sensor

[panacea]

I got twin Yamahas '95 70hp. On one motor the automatic rpm reduction kicked in a couple of weeks ago. I took it to the shop. They said it must be the temp sensor since I also have a temp gauge which shows the motor in normal temp range. Replaced sensor, problem persists. Also when I cold start the alarm buzzer comes on intermittently. It disappears when the motor is at operating temp. The mech at the shop said, 'must be the CDI unit'. I replaced that ($400). The buzzer still comes on when I cold-start. Checked all wiring - ok. Checked all electrical components - ok. Checked the buzzer by shorting it. Comes on continuously - so, ok. Now, what the heck is the problem there?

 

[bossee]

Re: Alarm buzzer - Temp Sensor

Thermostat? (check it is opening and opening at specified temp, can be tested in hot water and a tempguage, just hang the thermostat i a wire)<br />Any clogged cooling channels?<br />Impeller - how old?

 

[ianyoung77]

Re: Alarm buzzer - Temp Sensor

Could also be a problem in oil sensor. When it is buzzing disconnect the thermoswitch and see if buzzing stops. If it does then it is definitely overtemp and follow Bo's comments. If it keeps intermittently buzzing disconnect oil sensor. If this doesn't stop the buzzing it only leaves a wiring fault.

 

[ivar]

Re: Alarm buzzer - Temp Sensor

I'm with ian, could be oil sensor, if oil level drops to low on my 92 60hp, rpms are limited to 2000 and the buzzer goes off.

 

[TONY H]

Re: Alarm buzzer - Temp Sensor

Here's a Silly question: In regards to Oil Sensor...Is the oil reservior half empty when engine first starts? Maybe it isn't a cold start situation, maybe it's a low oil on first start-up.<br /><br />This has happened to me when my oil module was starting to go bad. Every once in a while the reservior would start to run down because it wasn't calling for oil from the big tank. <br />I would start the engine, buzzer would sound until Main reservior filled. I thought it was temperature related at first but no... oil

 

[panacea]

Re: Alarm buzzer - Temp Sensor

Ian had it right. It was the oil sensor. Here is what happened. The wires of the oil sensor got wedged between the oil reservoir and the power block. This way they chafed and with the vibrations they occasionally shorted setting off the overheat alarm. Now, apparently the wires remained in one position at all times after a while and set off the alarm buzzer with that intermittent noise at start-up. On checking the oil sensor I found that spot, insulated it, and the problem was gone. I will run the boat at high rpms tomorrow to check all operating ranges. Thanks guys.

 

[panacea]

Re: Alarm buzzer - Temp Sensor

Well, I thought the problem was over but when I ran the boat at high rpm the overheat sensor sounded. Since I also have a temp gauge and this showed normal temp I disconnected the temp sensor at the motor. I ran the boat for 50 miles without a problem. The temp gauge never even went to the middle of the gauge. The temp sensor is new, the cdi unit is new. The wiring seems to be ok. Now what could this be? Maybe the temp sensor is set too low so it sets in at a temp which would normally still be regular operating temp? Anybody have any idea?