2008 Evinrude E-TEC 55MFE Technical Manual, Page 177Get this manual
COOLING SYSTEM COMPONENTS Overcooling: Debris may prevent the valve from closing completely
Block Venting
A fitting and hose connected to the top of the exhaust cover allows the constant movement of water andor air from the blockCirculated water flows through the EMM and vapor separator before exiting through the overboard indicator
Pressure relief valve components
Thermostat
The thermostat is used to control water flow and operating temperature at lower speeds (below 1800 RPM)Overheating: restricted or faulty thermostat typically results in LOW SPEED overheatingOvercooling: Debris may prevent the thermostat from closing completely4 1