865900 Mercruiser SCREW, (.250-28 x .930)

The disconnect switch, if equipped, must be in the ON position to let the electrical system function. There will be damage to some of the charging circuit components if the engine is running with the disconnect switch in the OFF position.
If the vehicle has a disconnect switch, the starting circuit can operate only after the disconnect switch is put in the ON position.The starting circuit is in operation only when the start switch is activated.Alternator
Never operate the alternator without the battery in the circuit. Making or breaking an alternator connection with heavy load on the circuit can cause damage to the regulator.
The alternator is used to charge the storage battery during engine operation. The alternator is cooled by a fan that is a part of the alternator.The alternator converts mechanical energy and magnetic field into alternating current (AC) and voltage. This process is done by rotating an electromagnetic field (rotor) that is direct current (DC) inside a three-phase stator. The alternating current and the voltage that is generated by the stator are changed to direct current.Starting Motor
Illustration 1 g06135238
(1) Post for Battery Cable
(2) Terminal for Ignition Switch
(3) Solenoid
Illustration 2 g06135244
(4) Solenoid
(5) Plunger
(6) Mechanical Linkage
(7) Clutch
(8) PinionThe starting motor is used to turn the engine flywheel at a rate that will allow the engine to start running.The starting motor has a solenoid. When the ignition switch is turned to the START position, the starting motor solenoid will be activated electrically. The solenoid plunger will now move a mechanical linkage. The mechanical linkage will push the pinion to engage with the flywheel ring gear. The pinion will engage with the ring gear before the electric contacts in the solenoid close the circuit between the battery and the starting motor. When the circuit between the battery and the starting motor is complete, the pinion will turn the engine flywheel. A clutch prevents the starting motor from turning too fast.When the ignition switch is released from the START position, the starting motor solenoid is deactivated. The starting motor solenoid is deactivated when current no longer flows through the windings. The spring now pushes the plunger back to the original position of the plunger. At the same time, the spring moves the pinion gear away from the flywheel ring gear.Starter Operation
Illustration 3 g06135246The starter is activated when all of the following occur:
The Key Switch is turned to Start and all safety interlocks are met:
Mini Hydraulic Excavators: hydraulic lock control lever must be down
Compact Wheel Loader: parking brake must be engagedThe Machine ECM provides 12 V from pin 6 through 306 wire to the Engine ECM at V2-16. The Machine ECM provides 12 V to E1-21 to the start relay and ground to E1-36 to the start relay.With power and ground at the start relay connectors 2 and 5, the relay switches on and power from the main power relay turns the starter ON.Powering On the Engine ECM
Illustration 4 g06213902The engine ECM is powered ON when there is 12 V at V2-53, V2-55, and V2-56. Until that occurs Cat Electronic Technician (ET) will not be able to connect to the engine ECM and the engine will not start.The following will occur for the Engine ECM to be powered ON:The key switch is turned to ON and power is provided via the Main Power Relay and the 303 wire to the Engine ECM at V2-26.When the Engine ECM receives 12 V at V2-26, it sinks pin V2-41 to ground. This grounds G939 which provides the ground to the engine ECM relay at connector 5.The Engine ECM relay receives 12 volts from the 20A Engine ECM fuse.With power and ground at engine ECM relay connectors 2 and 5, 12 V is provided to the 150 wires and to the engine ECM at V2-53, V2-55, and V2-56.