An outboard motor is a boat engine that attaches to the outside of the boat's stern (the back end), rather than being built inside the hull. The motor sits in a metal bracket on the transom (the flat back wall of the boat) and can tilt up and down or swing from side to side.

Unlike car engines that sit under the hood, an outboard motor hangs off the back of the boat with its propeller underwater. The motor's weight sits outside the boat. This design has major advantages: you can easily remove the motor for repairs or storage, tilt it up in shallow water to avoid hitting rocks, and steer the boat by turning the entire motor left or right.

Small outboard motors might produce just a few horsepower and push a fishing boat across a quiet lake. Large outboard motors can power speedboats and generate hundreds of horsepower. You control an outboard motor with a handle called a tiller on smaller motors, or a steering wheel on larger boats.

Before outboard motors became popular in the early 1900s, small boats relied on oars, sails, or heavy inboard engines. Ole Evinrude invented one of the first practical outboard motors in 1909, making boating more accessible to ordinary people.