853213 Mercruiser THERMOSTAT

Table 1
Event Code    
Code and Description     Default Conditions which Generate this Code     System Response    
E539(1) High Intake Manifold Air Temperature     The intake manifold air temperature is above the trip point temperature for four seconds.     The warning lamp will illuminate, if equipped.
The code is logged.    
E539(2) High Intake Manifold Air Temperature     The intake manifold air temperature is above the trip point temperature for four seconds.     The warning lamp will illuminate, if equipped.
The code is logged.
Starting at
86 °C (189°F), the engine will be derated 10% for each one degree increase in temperature up to a maximum of 50%.    Probable Causes
Ambient air
Inlet air restriction and/or high altitude
Inlet air from a heated area
Inlet manifold air temperature sensor
Reduced flow of inlet air through the aftercoolerRecommended Actions
Ambient Air
Pressurized System: Hot coolant can cause serious burns. To open the cooling system filler cap, stop the engine and wait until the cooling system components are cool. Loosen the cooling system pressure cap slowly in order to relieve the pressure.
Determine if the ambient air temperature is within the design specifications for the cooling system and the aftercooler.
When the ambient temperature exceeds the capability of the cooling system or the aftercooler, operate the engine at a reduced load or operate the engine at a reduced speed.
If equipped, check the condition of the cooling fan and the drive belt. Verify that the cooling fan is operating correctly. Check for air in the cooling system and verify that the cooling system is filled to the proper level.
If necessary, clean the aftercooler and/or carefully straighten any bent fins.Inlet Air Restriction, Exhaust Restriction and/or High Altitude
Measure the intake manifold (boost) pressure while the engine is operating under load. For specific data, refer to the Technical Marketing Information (TMI) for the engine.
Replace any blocked air filters and/or remove any obstructions from the air inlet. Check for a restriction in the exhaust system.
Make sure that the settings for the engine are correct for the altitude.Inlet Air from a Heated Area
Ensure that the air inlet system is not receiving air from a heated area.
Check for air leaks in the pipe between the air inlet and the inlet to the turbocharger compressor.Note: If necessary, relocate the air supply to the inlet manifold to the outside of the engine enclosure.Inlet Manifold Air Temperature Sensor
Allow the inlet manifold air temperature sensor to cool and remove the sensor. Check the reading for the inlet air temperature. If the reading for the inlet air temperature and the ambient temperature are not approximately equal, replace the sensor.Reduced Flow of Inlet Air through the Aftercooler
Check for contamination in the air pipe that connects the turbocharger to the aftercooler.
Clean all contaminated air inlet pipes or replace all contaminated air inlet pipes.
Service the air cleaner and replace the air cleaner element.
If contamination is found in the air pipe from the turbocharger to the aftercooler, check all of the air inlet pipes upstream of the turbocharger for leaks.
If oil is found in the air pipe, inspect the turbocharger compressor housing and inspect the outlet from the turbocharger compressor for oil.
If oil is found in the inlet to the turbocharger compressor housing, the oil originates from the engine crankcase breather.
If oil is found in the outlet from the turbocharger compressor housing but oil is not found in the inlet to the compressor housing, the oil originates from the seals for the turbocharger bearings.