The outboard motor is used to propel the boat through the water at a speed faster than any set of oars. Motors come in various power levels, from small rowing boats to large fishing boats, although they all have a similar feature, that is, they are all independent propulsion systems connected to the boat; defender-class port patrol boats are propelled by dual outboard engines . Outboard engines have two power forms: electric and gasoline. Electric models are usually smaller and provide less horsepower in exchange for quieter sailing. They are good for small ships. On the other hand, gasoline-powered outboard engines are louder, but they can provide more power. For small boats, their starting power is as low as 2 or 3 horsepower, which can reach hundreds of horsepower to provide power for large fishing boats. Another possibility to increase power is that the boat has multiple outboard engines. It is not uncommon for a large fishing boat to have two or even four outboard engines all connected to the same steering wheel.
Outboard engines are generally very durable and can be expected to last for a long time. Gasoline-powered outboard engines have two-stroke and four-stroke engines. Four-stroke engines provide cleaner and smoother driving, while two-stroke engines are generally more powerful, but noisier and more polluting. Some water bodies only allow the use of cleaner and quieter four-stroke engines, and the future trend is the four-stroke model. High-performance speedboats, on the other hand, benefit greatly from the extra power, so two-stroke is always preferred. The outboard engine provides steering by actually turning. Some ships have a built-in rudder that can guide the flow of water even if the propeller is not turning. On larger ships, motors are sometimes attached to the steering wheel to provide the power needed to turn such large motors. Smaller outboard motors usually have a joystick, and the boatman can turn the joystick by hand to command the engine and the boat.
Outboard motors are usually very durable and can be expected to be used for a long time, but still need to be cautious. The two biggest threats are heat and carbon. Owners should always ensure that the engine's cooling system can resist heat. Most car exterior panels will flush the water they sit in to cool the engine, and a visible jet of water can be seen spraying from the engine. In order to reduce the carbon deposits in the engine, many additives can be added to the gasoline tank or handed over to the mechanic for repair. With these additives, outboard engines can provide vehicle owners with many years of service life.