Heat sensor for 91' 150HP Mercury/Mariner outboard

Answer 1

The 150 2 stroke heat sensor is loked on the starboard cylinder bank between the top and center cylinders
I is located between 2 head bolts and is held in place by  a plate that is hard to see. T he easiest way to find it is to follow the wire from the terminal block to the temperature sensor.  This wire often breaks or shorts out due to degradation of the insulation.  A new sensor comes with the wire.

Answer 2

I have a 115 mercury mariner and my heat sensor is located dead center on the back of the motor were the spark plugs are. of course they arn't the same but heat sensors pretty much just look like bolts to nowere, hope that helps