ELECTRIC SYSTEM

Electric System

Electric System

Introduction

This research describes typical electric starting circuits used in outboard motors and gives suggestions on diagnosing common problems. In order to make any meaningful investigation into electrical circuit problems, a basic understanding of electricity and a familiarity with making basic measurements of electric voltage is needed. If the reader lacks those skills, they should seek that knowledge before undertaking electrical diagnosis and repair.

Outboard motors are often fitted with electric motors for engine starting. In larger horsepower motors the electric starter motor is the only way to start the engine. Proper operation of the electric starter is therefore crucial. The circuitry which controls and actuates the electric starter motor is relatively simple, however it can be the source of frustrating problems. We examine the circuitry and offer some advice on diagnosis and repair of common problems.

The electric starter motor requires very high-current to operate. Because of this, it is operated by a control relay (commonly and hereafter called a solenoid) which is in turn controlled by an ignition switch. This arrangement divides the electric circuitry into two distinct segments, the low-current circuit associated with the ignition switch and the solenoid coil, and the high-current circuit associated with the starter motor. If your engine is a modern, modified, automotive unit it is likely to stop just like a petrol engine, when you turn the ignition off. To accomplish this is an electromagnetic solenoid valve is built into the injector pump. This type of valve needs a supply of current to allow the engine to RUN. This type also needs a supply of current to BLEED the fuel system. At some engines (Bukh) use a visually similar valve, built into the injector pump, which is only supplied with current to STOP the engine.

Discussion

Other manufacturers and mariners fit a solenoid to the injector pump's mechanical stop lever (where the stop cable would normally be fitted). Electrically this type of stop system requires a current supply to STOP the engine. If the engine were within two or three metres of the steering position I would say that the solenoid needs removing and being replaced with a stop cable. That way one ends up with a simple, robust system that does not suffer from wiring and other electrical faults. So if you have an electric stop control you need to find out if it needs current to STOP or current to run, once you have found that out, you can decide how to wire it up.

 

Current to RUN

As stated above, this type is most likely to be found on engines derived from cars and vans. We add the circuit to the starter diagram shown below.

Ideally this circuit will be fused because it carries current all the time the engine is running. However if the fuse blew, the engine will stop at once!

Current to STOP

In this case we need an ignition switch with an anticlockwise from OFF position on it - or a separate ...