1997 Johnson Evinrude "EU" 40 thru 55 2-Cylinder Service Manual, P/N 507265, Page 140Get this manual
Engine Temperature Check The Markal Thermomelt Stik is heat-sensitive marker that melts on contact with surface of specific temperatureOne source for Thermomelt Stiks is Stevens Instrument Company
At least two Thermomelt Stiks or digital pyrometer should be used to accurately determine the engine's operating temperaturesThe Thermomelt Stik mark will appear dull and chalky when the surface marked is below the Stik's rated temperatureWhen the surface exceeds the Stik's rated temperature, the mark will appear liquid and glossyTo achieve accurate and consistent readings, engine temperature must be gauged at the top of cylinder head
INote For the following engine operating temperatures and RPM
figures to be correct, the inlet water temperature must be 70 100 (21 30 C)Pyrometer Procedure
Avoid accidental starting of engine while changing propellers; twist and remove all spark plug leads1Install correct test propeller and place engine in test tank