38615 Mercruiser SCREW, (.250-28 x .750)

1.1 Starter
The starter is either an overhang type with the pinion sliding surfaces not exposed to the outside or a front nose type with them exposed to the outside. The overhang type is so constructed as to prevent entry of dust into the inside.This starter is makes up for loss of torque due to reduced size and higher speed or the motor proper by incorporation of a speed reduction gears. Namely, this starter is a reduction starter.Major components include: the motor that develops torque; overrunning clutch that transmits torque and prevents the starter from overrunning after engine start; magnetic switch that brings the pinion into mesh with the ring gear while turning on/off the load current to the motor; the reduction gear that reduces armature rotation speed and transmits increased torque to the pinion.(1) Reduction gear The end of the armature is a gear which is in mesh with the reduction gear so that the armature torque is increased and transmitted to the pinion.(2) Overrunning clutch A roller-type overrunning clutch is used.Rollers are housed in the wedge-shaped grooves formed by the outer and inner races (sleeve) and pressed by springs.When the starter is started, the roller is pressed towards the narrower side of the groove, functioning as a key to transmit rotation of the outer race to the pinion. No torque is transmitted, however, from the pinion (as it is turned by the engine), as the roller compresses the spring moving toward the wider side of groove and releasing the key action.(3) Operation While the starter switch is ON, current flows from the terminal "SW" of the starter relay to the terminal "L" and closes the contact "P2".When the contact "P2" closes, current from the battery flows from the terminal "S" of the magnetic switch to the pull-in coil "P" and holding coil "H". Furthermore, the current that has decreased flows from the terminal "M" to the motor section.The plunger, attracted by the magnetic flux of the pull-in coil and holding coil, closes the contact "P1" and simultaneously pushes out the pinion turning slowly on weak current. When the pinion comes into complete mesh with the ring gear, the contact "P1" closes and the large current of the battery directly flows to the motor section to turn the pinion powerfully.In this condition, no current flows to the pull-in coil "P".The plunger is retained by the holding coil "H" alone. When the starter switch is placed to OFF, current to the holding coil "H" is interrupted. The plunger is returned to its original position by the return spring and the contact "P1" opens so that current to the motor section is interrupted.The moment the starter switch is opened, the battery current flows from the terminal "B" to the pull-in coil "P" and holding coil "H". Since the coils are wound in opposite direction to each other, the magnetic fluxes cancel each other so that the return spring can move the plunger back to its original position.1.2 Alternator
(1) Model A2T72986, A4T57886, A4T57986, A2T32386, A6T75386 Alternator The alternator is a brush type in which a current flows from the brushes through the slip ring to the field coil in the rotor.Major components include: the rotor (field coil) that generates magnetic field; the stator that generates electromotive force; the rectifier that rectifies electromotive force so generated; the regulator that keeps generated voltage constant.(a) Charging circuit1) Setting the starter switch to ON 2) Starting the engine When the engine is started and the alternator starts generation so that the voltage at the alternator "B" terminal becomes higher than the battery voltage, the current flows as shown below. In this way, battery charge is started and at the same time, the charge lamp (if provided) goes out.(b) Rotor When the rotor is driven by the pulley rotation, a current flows from the brushes, through the slip ring, to the rotor coil. The rotor core tabs then become magnetic poles.(c) Stator Together with the rotor core, the stator core forms the magnetic flux path. The magnetic flux lines in the stator core are affected by the passage of the rotor core field and generate electricity.(d) Rectifier The rectifier mainly consists of 3 diode trios, 6 diodes and 2 heat sinks. It rectifies the AC stator output to DC power.Each heat sink has the (+) or (-) leads from 3 diodes attached to it, performing full wave rectification for 3-phase AC.(e) Regulator The IC regulator alters the strength of the field coil field to stabilize output power which varies with engine speed fluctuations.The regulator is integral with the brush holder. The assembly combines the IC regulator, the brushes and the brush springs.(2) Model A2T70772, A4T57472 Alternator The alternator is a brush type in which a current flows from the brushes through the slip ring to the field coil in the rotor.Major components include: the rotor (field coil) that generates magnetic field; the stator that generates electromotive force; the rectifier that rectifies electromotive force so generated; the regulator that keeps generated voltage constant.(a) Charging circuit1) Setting the starter switch to ON 2) Starting the engine When the engine is started and the alternator starts generation so that the voltage at the alternator "B" terminal becomes higher than the battery voltage, the current flows as shown below. In this way, battery charge is started.1.3 Vacuum Pump
The vacuum pump is installed on the back of the alternator and has its rotor coupled to the alternator shaft for simultaneous rotation with the alternator. Within its cylindrical housing, the rotor has three movable blades which are pressed onto the housing inner wall by centrifugal force generated as the rotor rotates, thus producing pumping action. The vacuum pressure generated by this action evacuates the vacuum tank. The rotor is positioned eccentrically to the housing cylinder. The air from the vacuum tank is sucked through the suction port and compressed gradually before it is discharged from the discharge port. From the suction port, engine oil is also sucked in to keep the