1991 Johnson/Evinrude Models "EI" 40 thru 55 Service Manual, Page 139Get this manual
Temperature Switch Test Purpose heat sensitive switch is installed in the cylinder head to monitor engine temperature This switch is connected in series with the warning horn If 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 position To ensure that the temperature sensing system can alert the operator during an overheating condition, it is very important that the warning horn be tested on regular basisSee Warning Horn Test, Section 1Testing 1Disconnect the bullet connector(s) and remove the temperature switch 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 switchf51 3Place the switch and an accurate industrial thermometer in E.J warm automotive crankcase oil4Slowly increase the oil temperature using an external heat source