1988 Johnson/Evinrude "CC" 40 thru 55 Models Service Manual, Page 161Get this manual
Pyrometer Procedure 1Install correct test propeller and place engine in test tank ill
'" To avoid accidental starting of engine while servicing, twist and remove all spark plug leads
2Start engine and run at 3000 RPM for at least five minutes
Reduce engine speed to 900 RPMAt 900 RPM, digital pyrometer should indicate 140 15 (60 C) when held on cylinder head If engine temperature is not within this range, troubleshoot cooling system to determine problem