1998 Johnson Evinrude "EC" 40 thru 55 2-Cylinder Service Manual, P/N 520206, Page 142Get this manual
Temperature Switch Test Purpose heat sensitive switch is installed in the cylinder head to monitor engine temperatureThis switch is connected in series with the warning systemIf the switch senses temperature in excess of predetermined limit, contacts close and cause the System Check gauge "WATER TEMP" light to turn on, and the warning horn to sound for ten seconds
INote To ensure that the temperature sensing
system can alert the operator during an overheating condition, test the warning system as described in Section 8, System Check Engine MonitorTesting
[] 1Disconnect the temperature switch and remove it from the cylinder head2Using continuity light or ohmmeter, make positive connections to the switchone lead to the switch lead and one lead to the metal portion of the switch[] 3Place the switch and an accurate industrial thermometer in warm automotive crankcase oil4Slowly increase the oil temperature using an external heat source