A first assistant engineer (also called the second engineer in some countries) is a licensed member

Licensed mariner

A licensed mariner is a person who holds a license issued by one or more countries to hold senior positions aboard ships, boats, and similar vessels. The United States Coast Guard grants licenses to members of the United States Merchant Marine in five categories: deck officers, engineers, staff...

 of the engineering department on a merchant vessel

Merchant vessel

A merchant vessel is a ship that transports cargo or passengers. The closely related term commercial vessel is defined by the United States Coast Guard as any vessel engaged in commercial trade or that carries passengers for hire...

. This title is used for the person on a ship

Ship

Since the end of the age of sail a ship has been any large buoyant marine vessel. Ships are generally distinguished from boats based on size and cargo or passenger capacity. Ships are used on lakes, seas, and rivers for a variety of activities, such as the transport of people or goods, fishing,...

 responsible for supervising the daily maintenance

Maintenance, Repair and Operations

Maintenance, repair, and operations or maintenance, repair, and overhaul involves fixing any sort of mechanical or electrical device should it become out of order or broken...

 and operation of the engine

Engine

An engine or motor is a machine designed to convert energy into useful mechanical motion. Heat engines, including internal combustion engines and external combustion engines burn a fuel to create heat which is then used to create motion...

 department. He or she reports directly to the chief engineer

Chief Engineer

In marine transportation, the chief engineer is a licensed mariner in charge of the engineering department on a merchant vessel. "Chief engineer" is the official title of someone qualified to oversee the entire engine department; the qualification is colloquially called a "chief's...

.

On a merchant vessel

Merchant vessel

A merchant vessel is a ship that transports cargo or passengers. The closely related term commercial vessel is defined by the United States Coast Guard as any vessel engaged in commercial trade or that carries passengers for hire...

, depending on term usage, "The First" or "The Second" is the marine engineer second in command of the engine department after the ship's chief engineer. Due to the supervisory role this engineer plays, in addition to being responsible for the refrigeration systems, main engines (steam

Steam

Steam is the technical term for water vapor, the gaseous phase of water, which is formed when water boils. In common language it is often used to refer to the visible mist of water droplets formed as this water vapor condenses in the presence of cooler air...

/gas

Gas

Gas is one of the three classical states of matter . Near absolute zero, a substance exists as a solid. As heat is added to this substance it melts into a liquid at its melting point , boils into a gas at its boiling point, and if heated high enough would enter a plasma state in which the electrons...

 turbine

Turbine

A turbine is a rotary engine that extracts energy from a fluid flow and converts it into useful work.The simplest turbines have one moving part, a rotor assembly, which is a shaft or drum with blades attached. Moving fluid acts on the blades, or the blades react to the flow, so that they move and...

, diesel

Diesel engine

A diesel engine is an internal combustion engine that uses the heat of compression to initiate ignition to burn the fuel, which is injected into the combustion chamber...

), and any other equipment not assigned to the Second assistant engineer/third engineer

Second Assistant Engineer

A Second Assistant Engineer or Third Engineer is a licensed member of the engineering department on a merchant vessel.The Second Assistant is usually in charge of boilers, fuel, auxiliary engines, condensate and feed systems, and is the third most senior marine engineer on board. Depending on...

 or the Third assistant engineer/fourth engineer

Third Assistant Engineer

The Third Assistant Engineer, also known as the Fourth Engineer, is a licensed member of the engineering department on a merchant vessel....

(s), he is typically the busiest engineer aboard the ship. If the engine room

Engine room

On a ship, the engine room, or ER, commonly refers to the machinery spaces of a vessel. To increase the safety and damage survivability of a vessel, the machinery necessary for operations may be segregated into various spaces, the engine room is one of these spaces, and is generally the largest...

 requires 24/7

24/7

24/7 is an abbreviation which stands for "24 hours a day, 7 days a week", usually referring to a business or service available at all times without interruption...

 attendance and other junior engineers can cover the three watch rotations, the first is usually a "day worker" from 0800-1700, with overtime

Overtime

Overtime is the amount of time someone works beyond normal working hours. Normal hours may be determined in several ways:*by custom ,*by practices of a given trade or profession,*by legislation,...

hours varying according to ship/company.

The first assistant/second engineer is usually in charge of preparing the engine room for arrival, departure, or standby and oversees major overhauls on critical equipment.