815803 Mercury PLUG

Monitoring the Trends of Engine Performance
For marine applications, the power demand can be difficult to determine. Consider the following factors for determining the power demand:
For propulsion with a water jet or a fixed propeller, the theoretical power is approximately proportional to the cubed engine speed.
Power demand at a given engine speed is dependent on several factors: loading of the vessel, weather, design of the hull and other conditions.To maintain a program for monitoring that is successful, several factors are important:
Record the data regularly when the engine is operating at similar loads and speeds.
Obtain accurate data.
At regular intervals, review the data in a graphic format.
Perform corrections before damage and/or downtime occurs.Accurate data is provided by accurate instruments and proper use of the instruments. The gauges and the sensing devices must be in good condition. This is especially true for thermocouples. Establish a program for calibrating the instruments periodically. Avoid using infrared thermometers for obtaining data. Be sure to read the gauges properly. Accurate recording of the data is also important.Use the following Steps to establish a program.
Establish a baseline for the engine parameters. The baseline is necessary in order to know the normal gauge readings. The new data will be compared to the baseline.
Use the data from the engine commissioning. The data is recorded for various loads. The data is recorded before any wear or deterioration takes place.
If there is no data from the engine commissioning, use data from the engine test cell. Understand that the data will not be specific to the site.
If data is not available from the engine commissioning or the engine test cell, calculate an average of the existing data.
Establish a new baseline after an overhaul.
Frequently record the new data during engine operation. For an example of a log to use, see this Operation and Maintenance Manual, "Hourly Performance Log" (Reference Information Section).Be aware that the readings of some parameters depend on the engine load. Record the data when the engine is operating at a high load. This increases the accuracy of the data. Also, any reduction in performance will be revealed sooner. A load of 75 to 100 percent is recommended.
For operations with a consistent load cycle, record the data at the same time for each day.
If the load can be controlled, set the load to the same amount for each reading.Some parameters that are NOT affected by the load ARE affected by the engine rpm. Obtain the readings for these parameters when the engine is operating at the same rpm.Some parameters are not affected by either the load or the rpm. See Table 1.
Table 1
Parameters of Engine Operation    
Parameters That Depend On the Load    
Aftercooler and oil cooler water temperature (outlet)    
Cylinder pressure    
Crankcase pressure    
Exhaust manifold pressure    
Exhaust manifold temperature    
Exhaust port temperature    
Inlet air restriction    
Inlet air temperature    
Inlet manifold air pressure (boost pressure) (1)    
Inlet manifold air temperature (1)    
Outlet temperature of the jacket water    
Parameters That Depend On the RPM    
Fuel filter differential pressure    
Fuel pressure    
Jacket water pressure    
Lube oil pressure    
Oil filter differential pressure    
Parameters That Are Independent of the Load and RPM    
Aftercooler and oil cooler water temperature (inlet)    
Inlet temperature of the jacket water    
Lube oil temperature    
( 1 ) This includes the air before the aftercooling and after the aftercooling. Note: A gauge reading that is abnormal may indicate a problem with operation or a problem with the gauge.
Illustration 1 g00747475
Example of a graph of engine oil pressure (Y) Pressure in kPa (X) Calendar days (1) Baseline (2) Operating pressure (3) Setpoint (alarm)
Average the data for each day. Use a computer or graph paper in order to produce a graph of the data. Compare the new data to the baseline. This will help to reveal the trends of the engine performance.Illustration 1 shows that the engine oil pressure was near baseline (1). Later, the operating pressure was approaching setpoint (3). The trend of operating pressure (2) indicated that the condition required investigation before activation of the alarm.
Compare the new data to the data from previous months. This comparison will be useful for scheduling reconditioning for the engine.Monitoring the Trends of Oil Consumption
The consumption of lube oil depends on the following factors:
Engine load
Hours of operation
Type of oilMonitor the engine's oil consumption by calculating the Specific Oil Consumption on a daily basis. Be aware that the following conditions can produce misleading data on oil consumption:
Improper operation of the lube oil centrifuge
Inaccurate measurement of additions of oil
Leaking of lube oil
Overfilling of the oil sumpTo measure additions of oil accurately, use a meter to monitor additions of oil at the engine. Also, check the total oil consumption against the delivery of oil.Calculating Specific Oil Consumption
Use the equation that is in Table 2 in order to calculate the Specific Oil Consumption.
Table 2
Equation For Calculating the Specific Oil Consumption    
    O ? D     = BSOC