1994 Johnson/Evinrude Outboards 40 thru 55 Service Manual, Page 147Get 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 Companyr,lAt least two Thermomelt or 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 glossyf21To achieve accurate and consistent readings, engine temperamust be gauged at the top of cylinder head For the following engine operating temperatures and RPM figures to be correct, the inlet water temperature must be 10 (21 30 e)
Pyrometer Procedure '" Avoid accidental starting of engine while changing propellers; twist and remove all spark plug leads