Construction and Working of Outboard Motor

Construction and Working of Outboard Motor
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In the earlier days, oars or sails were used to propel ships, especially the small boats. The small boats were of great use in the olden days for transporting goods and passengers. However, these small boats were extremely slow and thus not a favorable option in times of emergency or transporting perishable goods. Until the 20th century, the boats were still being propelled by oars and sails, but then the invention of outboard motors changed everything.

Outboard motors are small engines that are attached to the rear part of a boat. An outboard motor is almost similar in construction and working to a normal gasoline engine. A conventional engine used by an automobile or large ship consists of two, four or more cylinders, whereas an outboard engine uses only one cylinder.


The construction of an outboard motor consists of only one cylinder with a piston inside it. On the outside, the piston is attached to a piston rod which is then attached to a crankshaft. The crankshaft is connected to the main driving shaft, which is then connected to a small gear box. The gear box converts the vertical motion of the propeller to usable horizontal motion.

Outboard motor drawing


The working of an outboard motor is almost similar to that of a conventional engine. The single cylinder might either operate in a two-stage or four-stage cycle. A mixture of fuel and gasoline is burnt inside the cylinder which pushes the piston in the outward direction. As a result of the reciprocating motion of the piston, the crankshaft also moves, which thus moves the main drive shaft attached to it. The small gear box attached to the drive shaft converts the vertical motion of the propeller into usable horizontal motion.

To maneuver the boat, the whole motor casing is to be tilted, which is generally done manually. This makes the propeller spin at an angle, thus giving the needed direction. Some of the outboard motors can be tilted by hand, whereas some have a hydraulic system that connects the steering wheel and the motor.

4 stroke Outboard motor

Additional Information

Outboard motor boats are generally used for shallow or inland water ways. The engines are smaller in size and lighter in weight, thus making them easily portable. As the engine is attached to the boat just by a clamp, it can be easily removed and used for another boat.

However, some of the modern outboard motors are larger in size and have two to four cylinders. The new outboard motors can be electric, diesel or pump jet powered. Moreover, when not in use, outboard motors can be pulled up to take the propeller and lower unit out of the water, thus preventing them from getting damaged by sea weeds and underwater rocks.

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