1998 Johnson Evinrude "EC" 90, 115 SPL Service Manual, P/N 520209, Page 129Get 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 OMC Temperature Gun, PIN 772018, 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 temperature When the surface exceeds the Stik's rated temperature, the mark will appear liquid and glossy[] To achieve accurate and consistent readings, engine temperature must be gauged at the top of cylinder headTo troubleshoot and isolate cooling system problem properly, be sure to test both cylinder heads
INote For the following engine operating temperatures and RPM
figures to be correct, the inlet water temperature must be 70 100 (21 30 e)Pyrometer Procedure 1Install correct test propeller and place engine in test tank