An outboard engine is a type of propulsion system used on boats. It is mounted externally on the transom, or back, of the boat and combines the engine, gearbox, and propeller in one unit. This design allows for easy installation and removal, making it popular for small to medium-sized boats. Outboard engines come in various sizes and power outputs, typically measured in horsepower. They can be powered by gasoline or electricity, with many modern models offering improved fuel efficiency and reduced emissions. Common brands include Yamaha, Mercury, and Honda, each providing a range of options for different boating needs.