Describe a Starter-Motor Circuit.

Figure 1: Typical Starter-Motor Circuit.

A Starter-Motor Circuit: 

Figure 1 shows a very simple diagram of an engine starter-motor circuit. If one day you turn on the ignition switch, push the start button, and nothing happens, this is the circuit diagram you will need. A complete engine wiring diagram would probably contain the same information, but it would also contain all of the meters, idiot lights, and alternator wiring, adding considerable visual confusion.

For the starter-motor circuit all you need to see are the:

• Battery switch
• Fuse between battery switch common terminal and engine panel
• On/Off switch
• Momentary start switch
• Wire from starting switch to solenoid
• Heavy positive cable from battery-select common terminal to solenoid
• Heavy negative cable from battery negative terminal to engine negative terminal.

If the engine won’t turn over, the problem probably lies somewhere in this diagram. 

Source: Boatowner's Illustrated Electrical Handbook

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