853231 Mercruiser HOSE, Thermostat Housing To Heat Exchanger

Recommended Actions
Note: If the problem only occurs under certain conditions, test the engine under those conditions. Examples of certain conditions are high engine speed, full load and engine operating temperature. Troubleshooting the symptoms under other conditions can give misleading results.Diagnostic Codes, Event Codes and Derates
Certain diagnostic codes, event codes and/or derates may cause poor performance. Connect the Caterpillar Electronic Technician (ET) and check for active codes and/or for logged codes. Troubleshoot any codes that are present before continuing with this procedure.Cold Mode
Use Cat ET to verify that the engine has exited cold mode. Cold mode operation may slow throttle response.Parameters
Verify that the correct parameters are being used.Flash File
Verify that the correct flash file is installed.Throttle Signal
Monitor the status for "Throttle Position" on Cat ET. Verify that the status for "Throttle Position" is stable and that the engine is able to reach high idle speed. Refer to the appropriate diagnostic test for your application:
Troubleshooting, "Speed Control (PWM) - Test"
Troubleshooting, "Speed Control (Switch) - Test"
Troubleshooting, "Speed Control - Test"Electrical Connectors
Check for correct installation of the J1/P1 and J2/P2 Electronic Control Module (ECM) connectors and the unit injector connectors. Refer to service Troubleshooting, "Electrical Connectors - Inspect".Cylinder Performance
Check the valve lash and reset the valve lash, if necessary. Refer to Systems Operation/Testing and Adjusting.
Perform the "Cylinder Cutout Test" on Cat ET in order to identify any injectors that might be misfiring.
If Cat ET indicates a problem, remove the electronic unit injector from the suspect cylinder. Refer to Disassembly and Assembly.Note: Discard all fuel injection lines after use. Fuel injection lines must only be used one time.
Perform a compression test. Refer to Systems Operation/Testing and Adjusting. Possible causes of low compression are shown in the following list:
Loose glow plugs
Faulty piston
Faulty piston rings
Worn cylinder bores
Worn valves
Faulty cylinder head gasket
Damaged cylinder head
Check the following items for damage and/or wear:camshaft, valve train components and crankshaft and associated components.
Perform all necessary repairs. Ensure that the repairs have eliminated the problem. Unit Injectors
Perform the "Injector Solenoid Test" on Cat ET in order to determine if all of the injector solenoids are being energized by the ECM.
Perform the "Cylinder Cutout Test" on Cat ET in order to identify any injectors that might be misfiring. Refer to the circuit tests Troubleshooting, "Injector Solenoid - Test".
If Cat ET indicates a problem, remove the electronic unit injector from the suspect cylinder and install a new electronic unit injector. Refer to Disassembly and Assembly.Note: Discard all fuel injection lines after use. Fuel injection lines must only be used one time.
Ensure that the repairs have eliminated the problem. If there is still a problem, refer to the circuit test Troubleshooting, "Injector Solenoid - Test".Intake Manifold Pressure Sensor (Boost)
Monitor the status of "Fuel Position", "Rated Fuel Limit", and "FRC Fuel Limit" on Cat ET while the engine is operating under full load. These parameters should reflect the information below.
Table 1
"Fuel Position" = "Rated Fuel Limit"    
and    
"Fuel Position" < "FRC Fuel Limit"    If "Fuel Position" equals "Rated Fuel Limit" and "Fuel Position" is less than "FRC Fuel Limit", the electronics are operating correctly. Otherwise, proceed with the next Step.
Monitor the status of "Boost Pressure" and of "Atmospheric Pressure" for normal operation on Cat ET. When the engine is not running, the correct value for "Boost Pressure" is 0 kPa (0 psi).Turbocharger
Note: The turbocharger that is installed on this engine is a nonserviceable item. If any mechanical fault exists, except for the wastegate actuator (if equipped), then the turbocharger must be replaced. The wastegate actuator (if equipped) can be replaced.
Check the following items:
Check for correct installation of the turbocharger.
Check that the turbine blades rotate freely.
Check that the oil drain is not blocked or restricted.
Check that the housing for the turbocharger is free of dirt and debris.
Ensure that the wastegate (if equipped) on the turbocharger is adjusted correctly. Refer to Systems Operation/Testing and Adjusting.
If necessary, replace the turbocharger. Refer to Disassembly and Assembly.Air Inlet and Exhaust System
Observe the check engine lamp. Check for an air filter restriction indicator (if equipped). Clean plugged air filters or replace plugged air filters. Refer to the Operation and Maintenance Manual.
Check the air inlet and exhaust system for restrictions and/or leaks. Refer to Systems Operation/Testing and Adjusting.Fuel Supply
Visually check the fuel level. Do not rely on the fuel gauge only. If necessary, add fuel. If the engine has been run out of fuel, it will be necessary to purge the air from the fuel system. Refer to Operation and Maintenance Manual.
Ensure that the fuel supply valve (if equipped) is in the full OPEN position.
Contact with high pressure fuel may cause fluid penetration and burn hazards. High pressure fuel spray may cause a fire hazard. Failure to follow these inspection, maintenance and service instructions may cause personal injury or death.
Do not loosen any high pressure fuel lines when the engine is running. The high pressure in the fuel lines can cause personal injury or death. Wait 60 seconds after the engine has stopped to allow pressure to purge before any service or repair is performed on the engine fuel lines.
Check the fuel lines for the following problems: restrictions, collapsed lines, pinched lines and loose connections. If problems are found with the low pressure fuel lines, repair the lines and/or replace the lines. If the high pressure fuel lines have a leak, the high pressure fuel lines must be replaced. Refer to the Disassembly and Assembly manual.
Prime the fuel system if any of the following procedures h