862907 Mercruiser PROP NUT, Rear

Introduction
Do not perform any procedure in this Special Instruction until you have read the information and you understand the information.Identification of the smoke color is critical to establishing the cause of the issue. The different smoke colors are detailed below with the possible causes:Black Smoke
The likely causes of black smoke are:
Rich air to fuel ratio. Either not enough oxygen is being added to burn the fuel, or too much fuel.
During start-up, mechanical engines have fueling set to maximum. Maximum fueling can cause black smoke.White Smoke
The likely causes of white smoke are:
Incomplete combustion. Fuel not fully burnt before the end of the combustion process. The condition can also be caused by fuel being injected late in the combustion process. Cold ambient temperatures also contribute to inefficient combustion.
Incorrect fuel specification, water in fuel, or fuel starvation.
During start-up, the engine is cold and combustion is inefficient, which can cause white smoke.Gray Smoke
Gray smoke is a mixture of black and white smoke. Refer to sections "Black Smoke" and "White Smoke" for the causes.Blue Smoke
Note: Do not confuse blue smoke with white or gray smoke as blue smoke indicates a different engine problem.Instances of blue smoke are rare and are related to other faults.The likely causes of blue smoke are:
Excess lubricating oil in the engine cylinders.
Incorrect oil specification or excess oil.White, Gray, or Blue Smoke
If white, gray, or blue smoke is seen for a short period directly following instant load removal, the smoke is white smoke. The white smoke is caused by incomplete combustion.Operation at Altitude
The engine is designed for operation below 3000 m (9840 ft) above sea level. If the engine is operated above this altitude, more smoke will be generated. This situation is outside the design specification.To diagnose the cause of smoke, refer to the Systems Operation, Testing and Adjusting, Troubleshooting. In addition, for black or white smoke refer to the following procedures:Checks for Black Smoke
Note: If the machine is operating at more than 3000 m (9840 ft), the engine will emit more black smoke. The design specification is limited to altitudes of 3000 m (9840 ft) and below.
Perform a Two Pump Relief (2PR) Test as follows:
Elevate the stick and the boom to the fully lifted position.
Release the joysticks.
Quickly pull the two joysticks to stall the pump. A small amount of black smoke may be visible when operating at sea level. More black smoke will become visible at higher altitudes.
Quickly release the joysticks. Black smoke may become visible.On releasing the joysticks, any black smoke should clear once the engine speed has stabilized. If black smoke is still present at a stabilized engine speed, proceed to Step 2.
Check the engine intake and exhaust system for restrictions or blockages. Refer to Systems Operation, Testing and Adjusting, Air Inlet and Exhaust System - Inspect. Check the boost pipe for leaks. If no faults are found, proceed to Step 3.
Inspect the fuel injectors. Refer to Systems Operation, Testing and Adjusting, Fuel Injection Nozzle - Test. If no faults are found, proceed to Step 4.Note: Fuel measurement must be taken on the main return to tank fuel line. The measurement must be taken on a straight section of the fuel line close to the machine connection point.Note: The following measurement must be taken at low idle with minimum fuel in tank.
Use a suitable pressure gauge to measure the return fuel pressure. Record the pressure and fuel tank level on the claim story.If the return fuel pressure is more than 10 kPa (1.45 psi), contact the Dealer Solutions Network (DSN).If the return fuel pressure is less than 10 kPa (1.45 psi), install a replacement high-pressure fuel pump. If the fault is still present, contact the Dealer Solutions Network (DSN).Checks for White Smoke
White smoke may be present for less than 3 seconds when load is removed or after rapid acceleration. This situation is a known condition that does not affect engine durability. No further investigation is required.
If white smoke persists when starting a cold engine and does not clear as the engine warms, perform the following procedure:
Ensure that all inlet and return fuel valves are fully open.
Ensure that there are no fuel feed or return line restrictions.
Check the fuel inlet pressure. Refer to Systems Operation, Testing and Adjusting, Fuel System Pressure - Test.If no fault is found, proceed to Step 3.
Illustration 1 g06232958
Install a replacement coolant temperature switch as follows:
Drain the engine coolant. Refer to Operation and Maintenance Manual, Cooling System Coolant (ELC) - Change.
Disconnect cable (2) from switch (1).
Remove switch (1) from the cylinder head.
Install switch (1) in the cylinder head. Tighten the switch to a torque of 16 N m (142 lb in).
Connect cable (2) to switch (1).
Refill the engine coolant. Refer to Operation and Maintenance Manual, Cooling System Coolant (ELC) - Change.
If the fault is still present, continue to Step 4.
Check and adjust the valve lash. Refer to Systems Operation, Testing and Adjusting, Engine Valve Lash - Inspect/Adjust. If no fault was found, proceed to Step 5.Note: Fuel measurement must be taken on the main return to tank fuel line. The measurement must be taken on a straight section of the fuel line close to the machine connection point.Note: The following measurement must be taken at low idle with minimum fuel in tank.
Use a suitable pressure gauge to measure the return fuel pressure. Record the pressure and fuel tank level on the claim story.If the return fuel pressure is more than 10 kPa (1.45 psi), contact the Dealer Solutions Network (DSN).If the return fuel pressure is less than 10 kPa (1.45 psi), install a replacement high-pressure fuel pump. Ensure that the old pump is retained as a "Send It Back" (SIB) request will be raised for the return of the fuel pump. If the fault is still present, contact the Dealer Solutions Network (DSN).Checks for Blue Smoke
If excessive blue smoke is present, investigate the cause. Monitor the engine oil consumption. Refer to Systems Operation, Testing and Adjusting. Obtain an oil sample analysis. Refer to Operation and Maintenance Manual.