1996 Johnson/Evinrude Outboards 50 thru 70 3-Cylinder Service Manual, Page 146Get 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
least two Therl:nomelt Stiks or digital pyrometer should be used to accurately determine the engine's operating temperatures
The 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 headFor the following engine operating temperatures and RPM figures to be correct, the inlet water temperature must be 70 10 (21 C)Pyrometer Procedure 1Install correct test propeller and place engine in test tank'" Twist and remove spark plug leads before changing propellers to avoid accidental starting of engine2Start engine and run at 3000 RPM for at least five minutes3Reduce engine speed and run engine at 900 RPM for five minutesAt 900 RPM, digital pyrometer should indicate 140 15 (60 C) when held on the cylinder head If engine temperature is not within this range, troubleshoot cooling system to determine problem4Increase engine speed to 5000 RPMAt 5000 RPM the digital pyrometer must not indicate more the 160 (71 C) If engine temperature exceeds 160 (71 C), troubleshoot cooling system to determine problemIf you get low or inaccurate readings during these tests, coat the probe location with liberal amount of Wakefield Heat Sink Compound, OMC PIN 322170