2007 Evinrude E-Tec 75, 90 HP outboards Service Manual, Page 194Get this manual
COOLING SYSTEM ENGINE TEMPERATURE CHECK IMPORTANT: If you get low or inaccurate readings with digital pyrometer, coat the probe location with Thermal Joint Compound, PN 322170Check thermostat for cracks, heat damage, or signs of corrosionCheck for proper operationThermostat opens at 143F (62C)Refer to THERMOSTAT SERVICING on p199 Pressure Relief Valve Inspection
The pressure relief valve should be closed at IDLE speedWater should not flow past the plunger and sealIf IDLE temperature is too low, check pressure relief valve plunger and seal for damage or debris that could prevent the valve from closing completely
Thermostat housing
IMPORTANT: Digital pyrometer or temperature
gun measurements may be slightly lower than software temperature readings
If IDLE temperature is still below operating range, replace pressure relief valve assembly and plunger sealTo test pressure relief valve operation, monitor temperature at the thermostat housing with Temperature Gun, PN 772018, or digital pyrometerConfirm normal IDLE operating temperatureSlowly increase engine speed from IDLE, up through 2500 RPMEngine temperature should decrease from normal IDLE temperatures as pressure relief valve opensValve should open between 1800-2200 RPMIf temperature decreases at lower RPM, replace pressure relief valve assemblyRefer to PRESSURE RELIEF VALVE SERVICING on p200