1997 Johnsoon Evinrude "EU" 50 thru 70 3-Cylinder Service Manual, P/N 507266, Page 144Get this manual
Temperature Switch Test Purpose One heat sensitive switch is installed in the cylinder head to monitor engine temperatureThe 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
To ensure that the temperature sensing system can alert the operator during an overheating condition, test the warning system as described in System Check Engine Monitor, Section 8Testing
rn 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