1990 Johnson Evinrude "ES" 9.9 thru 30 Service Manual, P/N 507871, Page 132Get this manual
Temperature Switch Test Purpose heat sensitive switch is installed in the cylinder head to monitor engine temperatureThe switch is connected in series with the control box warning hornIf the switch senses temperature in excess of predetermined limit, contacts close and cause the warning horn to sound continuous tone when the key switch is in the ON positionTo ensure that the temperature sensing system can alert the operator during an overheating condition, it is very important that the control box warning horn be tested on regular basisSee Warning Horn Test, Section 1Testing
f41 1Disconnect the bullet connector(s) and remove the temperaswitch 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