Ship engineers operate engines and other equipment on many types of ships.

Ship engineers operate and maintain propulsion engines. They also run machinery such as:

• Boilers
• Generators
• Pumps

A typical deep-sea merchant ship has four engineering officers. These include a chief engineer and a first, second, and third assistant engineer. The size and service of the ship determine the number of the crew for a voyage. Small vessels may have only one engineer or none.

Ship engineers regulate the engines to control the speed of the ship. They keep records of what they do in engineering logs. They note changes in the ship's speed and direction.

Assistant engineers stand periodic watches. They oversee the safe operation of the engines and machinery. They test machinery and equipment to make sure everything is running properly.

Ship engineers inspect and maintain the engines and other equipment. They order spare parts and oil as well as maintain inventories. They clean and repair machinery using hand or power tools. They may direct qualified members of the engine department (QMEDs) to repair or replace defective parts. QMEDs work in the engine spaces below the decks, under the direction of the ship's engineering officers. They may operate pumps and valves.

Engineers often participate in safety drills to practice what to do in an emergency.