Starter Motors

Lecture contents:

1. Starter Motor Introduction
2. Video Lesson
3. Summary
4. Quiz

Estimated study time 30 Minutes.

1) Starter Motor Introduction

Starter motors are incredibly high current devices yet they are the only electrical devices on board that can be connected to their batteries with absolutely no fuse!

As such, your vessels engine starter motor wiring must be in top condition, regularly inspected, and well maintained, not just to ensure reliable starting, but to prevent fire risks too.

A thorough understanding of the mechanism of, and the wiring to your starter motor could help get you out of a few tricky situations at sea, or better still, help you identify potential problems before they become faults.

Most faults with starting circuits emanate from a lack of maintenance to the:

1. Batteries
2. Battery terminals
3. Engine Negative connection (ground)

As mentioned earlier in the course, all connections between the start battery and the starter motor, must be periodically checked, cleaned and coated with dielectric grease. Whilst checking ensure that the cables are not chafing and the insulation is not wearing through, this could cause a fire.

Even something as simple as a partially flat battery can cause the starter to become jammed, the video lesson below includes a couple of work arounds for this problem.

The lesson below covers how the starter motor works, how its wired and how to find and repair common faults with your engine starting system, but remember - prevention is better, in all but a handful of cases a faulty starting system is due to lack of maintenance.

At this stage of the course you should be familiar with batteries, relays, solenoids, cleaning and testing connections, and using the multimeter, and clamp meter, from the previous lessons, if not please complete those sections first.

2) Video Lesson

3) Summary

The Engine Starting Process.

Each time you press the start button you initiate a cascade of events.

1. The start button connects power to the start relay
2. The start relay connects the power to the start solenoid
3. The start solenoid connects power to the starter motor

Each of the above processes should be thought of as stand alone circuits, that can be tested individually, the first process is simply a start button powering an electromagnetic coil in a relay, nothing complicated. The second process is simply another circuit powering a solenoid, and the third is yet another circuit providing power to the starter motor. Diagnosing and testing requires us to reduce seemingly complex wiring down to the lowest denominator, ultimately even the most complex of wiring boils down to a collection of very simple single circuits.

4) Quiz

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