How outboard motor controls work

Written by john garrison
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Outboard motors are the simplest engines available. They are a step above a lawnmower engine because they do contain a simple transmission, but the technology behind their control systems is still fairly easy. The entire system consists of the gear selection switch, the throttle, and the kill switch. The motor also has systems in place to allow it to function as steering device for the craft.

Gear Selection

Unlike your car, your boat doesn't need to change gears while on the move. This allows for a much more simple transmission system than the one in your automobile. An outboard motor only has three gears, forward, reverse, and neutral. Since there is never a need for the gears to be changed while moving, the shift lever on an outboard simply moves the gears into place with simple mechanical means. The shift position on the outboard's throttle handle throttles the engine down. As long as the user is gentle with the controls, the gears will easily slide into position without grinding.


Very similar to a motorcycle, an outboard's throttle handle is connected to a throttle cable. As the handle is twisted, the throttle cable is pulled. The other end of the throttle cable is attached to the carburettor, or in more modern motors the throttle body. When the cable is pulled, it pulls a lever allowing more gas and air to enter the engine. The more gas that is allowed into the engine, the more force the explosion, and the faster the engine moves.

Cut-off Switch

All gasoline motors rely on a spark to function. The spark plug ignites the gas, which pushes the piston down. This spark is powered by an electrical circuit. Even if a motor doesn't have a battery, like an outboard, it still has an on-board electrical system. In the case of an outboard motor, the power is provided by a device known as a magneto. The stop switch, or kill switch, on an outboard motor simply stops the flow of electricity to the spark plugs. Without a spark, the gas will not ignite and the engine will no longer run.


Some, if not most, boats which use outboard motors also rely on those motors to provide the steering mechanism for the craft. This is accomplished very simply by attaching the motor to the boat using a tube within a tube, exactly the same as the front wheel on your bike. Steering the boat is the opposite of steering a car. If you push the engine to the right, the propeller actually turns to the left. You can visualise how this works by imagining a bicycle being ridden backwards, with its steering mechanism behind it like a boats.

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