824941 Mercruiser SCREW (3/4")

Operator Information
Obtain the following information from the operator:
The problem and the time of the occurrence
Determine the operating conditions for the occurrence.
Determine if there are any systems that were installed by the customer that could cause the symptom.
Determine whether any other symptoms happened in addition to the problem.Note: If the problem only occurs under certain operating conditions (high idle, full load, engine operating temperature, etc), test the engine under those conditions.Other Symptoms
If other symptoms occurred in addition to the problem, determine whether the other symptoms are related to the problem. Determine whether the symptoms and the problem have a probable cause that is common. For example, high engine oil pressure and excessive consumption of engine oil can be caused by the use of incorrect engine oil.Report the Service Information
After you have successfully repaired the engine, it is important to provide good information about the repair. The following topics are recommended for your report:Complaint - Include a description of the customer's complaint in the report.Cause - Provide a specific description of the cause of the failure. Include the method that was used in order to diagnose the problem. Indicate your determination of the problem. If you performed a test, identify the test procedure. For example, a visual inspection revealed abrasion of a wire in a harness. Be specific: testing of the engine produced power below specifications at 1000 rpm due to the loss of a fuel injector.Repair - Explain your repair of the problem. For example, you may have installed a new wiring harness. You may have replaced the fuel injector per instructions from the factory.Providing complete, accurate information will help Caterpillar to provide better service to you and to the customer.Combustion Noise (Knock)
Probable Causes
Incorrect fuel injector timing
Problem with a fuel injectorRecommended Repairs
Fuel Injector Timing
If the fuel injector timing is incorrect, the fuel will be supplied to the cylinders at the wrong time. This can cause combustion noise (knock). Make sure that the fuel injector timing is correct. Refer to Testing and Adjusting, "Fuel Injector Timing".Fuel Injector
If a fuel injector is leaking, the fuel will be supplied to the cylinder at the wrong time. This can cause combustion noise (knock). Check the cylinders' exhaust port temperatures. A high temperature can indicate that the cylinder is receiving too much fuel. If the exhaust temperature of any cylinder has a difference of 50 °C (90 °F) from the average exhaust temperature of all of the cylinders, there may be a problem with the fuel injector. Replace the fuel injector.Coolant in the Engine Oil
Probable Causes
Engine oil cooler
Cylinder liner
Cylinder blockRecommended Repair
Engine Oil Cooler
If coolant is leaking into the lubrication system through the engine oil cooler, replace the engine oil cooler. Change the engine oil and replace the engine oil filters.Cylinder Liner
If there is a problem with the seals for the cylinder liner, replace the seals.If a cylinder liner is cracked, replace the cylinder liner.Cylinder Block
If you suspect that the cylinder block is leaking, pressurize the cooling system in order to locate the leak. Inspect the cylinder block for cracks and/or other damage. If a problem is found, install a new cylinder block.Excessive Black Smoke or Gray Smoke
Probable Causes
Inlet air restriction
Excessive consumption of fuel
Incorrect fuel injector timing
Problem with a fuel injector
Problem with an exhaust valveRecommended Repairs
Inlet Air Restriction
The inlet air must be sufficient for combustion. The maximum allowable inlet air restriction is 3.75 kPa (15 inches of H2O). Replace the soot filters and check the air restriction again. If the inlet air restriction is still too high, inspect the inlet air piping for obstructions.Fuel Consumption
Refer to "Excessive Fuel Consumption".Fuel Injector Timing
If the fuel injector timing is incorrect, the fuel will be supplied to the cylinders before the air is sufficient for complete combustion. Make sure that the fuel injector timing is correct. Refer to Testing and Adjusting, "Fuel Injector Timing".Fuel Injector
Check the cylinders' exhaust port temperatures. A high temperature can indicate that the cylinder is receiving too much fuel. If the exhaust temperature of any cylinder has a difference of 50 °C (90 °F) from the average exhaust temperature of all of the cylinders, there may be a problem with the fuel injector. Replace the fuel injector.Exhaust Valve
Inspect the condition of the exhaust valves. Replace any exhaust valve that is damaged.Engine Oil in the Cooling System
Probable Cause
Leaking engine oil cooler coreRecommended Repair
If the engine oil is leaking into the cooling system through the engine oil cooler, replace the engine oil cooler.Excessive Consumption of Engine Oil