15HP Yamaha overtemp light

[ScoutB]

I picked up a 2017 Yamaha 15HP for a good price, but I'm fighting a "overtemp" issue. It runs fine at full throttle for a minute or so, then the overtemp light comes on on the motor cuts power but lets me idle home. Water pump is new, telltale squirts perfectly. I replaced the thermostat but nothing changed. I messed around with it over the weekend and discovered that shutting it off and immediately restarting clears the light and I can go full throttle again for a minute again. Over and over. Makes me think it's an electrical problem. if it was actually overheating it wouldn't cool down in the 3 seconds it's off. Another oddity, I can go at half throttle forever without the light coming on. Any suggestions for the next step would be appreciated.

 

[99yam40]

all I can think of is to do a chemical clean of the motor, good chance there is a buildup in the cooling passages. WOT burns more fuel and creates more heat.

and it is not a good idea to keep running a motor that is overheated .
the motor lets you know there is a problem, so you need to shut it down when it is safe to do so.

use a Infared gun to measure the temp of the motor where the temp sensor is located to see what temp it is getting up to would be a good idea.
you can always pull that switch out and test it to make sure it is operating in spec

 

[ScoutB]

all I can think of is to do a chemical clean of the motor, good chance there is a buildup in the cooling passages. WOT burns more fuel and creates more heat.

and it is not a good idea to keep running a motor that is overheated .
the motor lets you know there is a problem, so you need to shut it down when it is safe to do so.

use a Infared gun to measure the temp of the motor where the temp sensor is located to see what temp it is getting up to would be a good idea.
you can always pull that switch out and test it to make sure it is operating in spec

Thanks. Do you know where to look up that temperature spec?

 

[99yam40]

service manual for your motor will have the specs.

I would think most motors would be the same, but I cannot say that is true

 

[dingbat]

if it was actually overheating it wouldn't cool down in the 3 seconds it's off.

The alarm is reset each time the ignition is energized at start-up.

Jumper out the temp switch to see if the problem goes away

 

[ScoutB]

The alarm is reset each time the ignition is energized at start-up.

Jumper out the temp switch to see if the problem goes away

Thanks, I'll try that.