How Does a Boat Motor Work?

by Steve Smith

Motor Design and Function

A boat motor works like a car engine. It contains a series of piston heads in cylinders that move up and down. These pistons are connected to a crank shaft, which is turned as the pistons move up and down. The force that drives the pistons and causes them to move up and down is a small explosion of gasoline or diesel fuel. The more fuel pumped into the cylinders, the faster the pistons move and the faster the motor crank shaft spins.

Drive System

A boat motor receives fuel through a pump just like in a car. The pump is connected to a tank that holds the gas. When the throttle is turned up, the tank pumps more fuel into the engine. In addition, the throttle valves open allowing more gasoline into the engine. The crank shaft is connected to a drive rod, similar to that of a car. This rod is eventually connected to a propeller causing it to spin. Most boats have only a forward (spin to the right) and reverse (spin to the left) transmission. The transmission will switch the drive of the propeller into forward or reverse.


A big difference in car and boat motor is the cooling system. A boat motor will use water to cool the engine. Some advance boat motors may also use antifreeze. The water is supplied to the engine by an exterior pump. It is flushed through the motor and then expelled by the cooling system. It exits the boat through holes which are usually located in the stern (rear) or the vessel. The water and exhaust both exit through these exhaust ports.

About the Author

Steve Smith has published articles on a wide range of topics including cars, travel, lifestyle, business, golf, weddings and careers. His articles, features and news stories have appeared in newspapers, consumer magazines and on various websites. Smith holds a Bachelor of Arts in English and journalism from University of New Hampshire Durham.

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