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Yamaha engines overheating

R

ron100

New member
"I have just purchased a new b

"I have just purchased a new boat with two new Yamaha 150's and digital guages. I am having a problem with overheating. The guage says the motor is getting hot, but an infra-red reading of the thermostat housing says the motor is normal temperature. The dealer has confirmed through lake testing that the sensors are sending a 'hot' temperature but the motor isn't really hot. My next step is to take the boat out again for a more extensive lake test, but I am not sure where to go from here.

Has anyone experienced any issues with Yamaha sensor or guage failures?"
 
"disconect the sensors and see

"disconect the sensors and see what happens, if the gauge doesnt say the motors getting hot, then it must be one of the sensors."
 
"Here is an update that I hope

"Here is an update that I hope will be helpful to other Yamaha owners as well. The F150 motors have the Command Link square tachometer gauges. The temperature indicator will only display five positions. The middle (third) position is normal, and that is where it runs at 3,000 rpm or below. At 4,000 rpm or above, it will run in the 4th (warm) position. I have run it for several hours now above 5,000 rpm (about 50 miles in 68 degree water) and could not get the motor to go to position 5 (overheat). Yamaha customer service has told me that it is normal for these engines to run in the 'warm', or 4th position, while cruising.

What surprised me is that the sensor for the tachometer gauge is not even close to the thermostat or measures the actual motor temperature. The tachometer gauge sensor is on the other side of the motor from thermostat, and is on a raised mounting block. As an engineer, it is hard for me to see what is actually being sensed as it is measuring a small block on top of the motor which is surrounded by air. The temperature of this gauge sensor is very different than that of the thermostat. So the gauge only gives an indication of motor temperature and can display something very different from the actual temperature of the motor. An infra-red reading while the gauge indicated a 'warm' condition (position 4) showed the thermostat is 135 degrees, and the sensor block for the gauge is around 200 degrees. The technician at the dealer says that anything under 266 degrees for the sensor gauge is acceptable.

In summary, the gauge is only an indication of motor temperature. The true temperature is controlled by the thermostat which also controls the overheat alarm. You cannot tell from the gauge how close you are to an alarm or overheating condition as you go from warm (position 4) to alarm (position 5). Running in the warm position is considered normal.

I hope this is helpful to other Yamaha owners. Thanks to everyone for all your suggestions."
 
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