Suzuki 2002-2005 DF4/DF5/DF6 4-Stroke Outboards Service Manual, Page 99Get this manual
6-32 POWER UNIT
THERMOSTAT
If salt deposits, corrosion, wear or other damage is found, clean or replace the thermostat
Thermostat operation Check the thermostat operating temperature as follows1Insert length of thread between the thermostat valvebody and suspend the thermostat in container filled with water2Place the thermometer in the container and heat waterObserve water temperature when the thermostat valve opens and releases the threadThermostat operating temperatureStandard48 52C (118 126F)