87156 Mercruiser BEARING ASSEMBLY, Roller

1. Engine tachometer2. Engine oil pressure3. Fuel pressure4. Engine oil temperature5. Engine jacket water temperatureThe tachometer (1) monitors the engine RPM.Oil pressure reading (2) will be the greatest after starting the engine. Oil pressure will decrease as the engine warms while idling. As the engine speed is increased to the full load speed, oil pressure will increase into the NORMAL range and stabilize.The fuel pressure gauge (3) indicates pressure of the filtered fuel. If the fuel filter gauge registers OUT, clean the primary fuel filter, if so equipped. Install new fuel filter elements.The purpose of the oil is to lubricate all moving parts inside the engine and to cool (remove the heat from) the pistons, liners, and bearings. Gauge (4) indicates the engine oil temperature.Gauge (5) monitors engine water temperature. This gauge may vary according to the load, but should never exceed the boiling temperature for the system being used.Emergency Shutoff Devices and Alarms
Alarms and Shutoff Devices
Alarm systems provide either an audible or a visual warning, or both, when certain abnormal operating conditions occur. These conditions can be low fuel supply, low oil pressure, or high engine coolant temperature. The alarm will be activated until the cause for the condition is corrected. The alarm sensor will then return to its normal position, and shut off the alarm circuit.If no action is taken when the alarm is activated for lack of lubrication or coolant, the engine can be damaged. To prevent this from occurring to unattended engines, shutoff devices should also be used.At a slightly different temperature or pressure range than that which activates the alarm system, the shutoff device stops the engine. The Engine Failure Light on the control panel and one or more of the indicators will either light, or pop out to indicate the problem. Repairs must be made before starting is attempted.Electronic Overspeed Shutoff Switch
This switch uses a magnetic pickup mounted in the flywheel housing to sense engine speed.Low Oil Pressure Shutoff Switch
This device is usually mounted on the side of the engine with oil lines connected to the switch. Low oil pressure closes the switch. Manually operated systems require resetting by pushing the button until it latches. After the engine starts and develops oil pressure, the oil pressure will push the button to the extended running position.
If the reset knob does not move to the extended position after the engine starts, the engine will not be protected by this switch.
If the button remains in the reset position, the engine oil pump is not developing normal oil pressure and a check should be made.Automatic start-stop systems use a pressure switch which resets itself.Overspeed Shutoff
Should the engine overspeed, the magnetic pick-up will close the circuit to the fuel shutoff solenoid and stop the engine.The shutoff switch can be checked for proper operation at 75% overspeed condition:1. Determine the full load RPM of the engine from the serial number plate.2. Operate the engine at the speed shown in the OVERSPEED TEST RPM Column of the chart. 3. While maintaining test RPM, push and hold the VERIFY button. The engine should stop.If the engine does not stop at the specified test RPM, contact your Caterpillar dealer. As the engine stops, the yellow light (2) will go on. The RESET button (1) must be pushed before starting the engine.Electronic Overspeed Shutoff Switch With Cranking Termination
After the starting motor has cranked the engine, the pinion gear can remain engaged with the flywheel as engine speed increases. At 600 RPM, the magnetic pickup opens the circuit to the starter motor, which allows the pinion to disengage. The circuit remains open until the flywheel stops. This prevents energizing the starter motor again while the flywheel is turning.This switch has a 75% VERIFY button (1), a RESET button (2) and an indicator light (3) similar to the speed switch. The operation of this portion of the switch is identical in all respects to the one just described.In addition, this switch has a second sensing circuit. This prevents the starter pinion from remaining engaged in the flywheel at excessive RPM.Overspeed Shutoff Switch (Electro-Mechanical)
This switch is mounted either on the tachometer drive or on the governor. Excessive engine speed closes the switch by centrifugal force. To reset the switch, push the button marked RESET. The knob will remain down until the engine overspeeds.Alarm Switches
Alarm switches are set at a less critical temperature, pressure, or level limit than the comparable shutoff control. The alarm switch warns the operator that an unsafe operating condition is starting to occur. Corrective measures should be taken to avoid possible damage to the engine and/or a possible shutdown of the engine.
It could be hazardous to have the engine stop unexpectedly when engine power is needed. However, if the engine overspeeds, the engine must be stopped immediately.
When the preset temperature, pressure or fluid level occurs, the alarm switch will either turn on a light or an audible alarm. The light or alarm will continue to operate until the condition is corrected. When the condition is corrected the alarm will automatically reset and the light will turn off.
The cause of the shutdown must be investigated and corrected before starting the engine.
Alarm Shutoff Switch
A switch may be installed in the alarm circuit for silencing the alarm while the engine is stopped for repairs. Before starting be sure the switch is moved to the closed (ON) position and the warning lights are lit.
If the switch is left in the open (OFF) position when the engine is started, the engine will not be protected.
Testing Shutoff Devices and Alarms
Have all shutoff controls and alarms on the engine checked twice a year by your Caterpillar dealer.It is important that these controls function properly. Their operating condition can only be checked by simulating extreme operating conditions under controlled testing procedures. To avoid damage to the engine, only authorized personnel should conduct these checks.Most control panels are equipped with a test switch. By turning the switch ON, all of the indicator lights can be checked for proper operation. Test the