1975 Evinrude 2HP Model 2502 Full Factory Service Manual, Page 35Get this manual
CHECKING MOTOR TEMPERATURE
The motor may be checked for overheating with the use of the Markal
Thermomelt StikThis is heat sensitive stick, similar to crayon,
which melts on contact with surface at specific temperatureThe motor is best checked when operating on boatIT this is not possible, run the motor in test tank for at least five minutes, at maximum speed of 3000 rpmUsing 163Thermomelt Stik, mark the starboard side of the cylinder with the StikSee Figu 5-2
REFER ENCE PICTURE
DO NOT use the stick on the cylinder headThe center of the cylinder head will normally run Slightly hotter than 163' FahrenheitThe mark will appear dull and chalkyIT the mark melts and appears glossy, the power head is overheatingCheck for worn water pump or
a clogged or eaky cooling system(See Section 6, Lower Unit)
Figure 5-2CheCking Motor
Temperature
REMOVAL OF POWER HEAD