Cruise Ship Engine Room (Everything You Want to Know)

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Cruise ship engine room interior with water tight doors electrical and diesel engines, water pipes, measuring instruments

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Cruise ships require a lot of power to sail and operate. The cruise ship engine room is both mysterious and fascinating because it’s hidden from passengers.

Passenger ships have come a long way from sails and steam engines. Modern cruise ships use diesel-electric engines, while newer cruise ships are moving towards more environmentally friendly solutions like liquified natural gas.

Here’s everything you need to know about a cruise ship’s engine room.

Where is the Cruise Ship Engine Room?

Cruise ship engine room interior with water tight doors electrical and diesel engines, water pipes, measuring instrumentsPin

The engine rooms on cruise ships are located on the lower decks, between the midship and the aft. The engines aren’t quite at the back of the vessel but closer to midship.

There are several reasons for keeping the cruise ship engine room away from passenger areas.

  1. Stability: Placing the engines and heavy equipment below sea level helps keep the ship stable and prevents cruise ships from tipping over.
  2. Noise: Engine rooms are extremely noisy. Naval engineers compensate by incorporating sound reduction features and noise dampeners. However, the sound and vibration wouldn’t be pleasant for cruise ship passengers.
  3. Security: The engine room spaces are in crew-only areas for safety and security purposes.

Most of the heavy machinery on a cruise ship is located on the lower decks, just above the keel. The positioning of the engine room, other machines, and technical equipment give the massive vessels a lower center of gravity.

The interor of an engine room on a large passenger vesselPin

Although you might envision the engine room as a massive open room running the ship’s length, the lower decks are divided into several water-tight compartments. One compartment may house the cruise ship water fresh water systems, another for the main engines, and another for the air conditioning.

The division of the engine room into separate compartments is for safety. Dividing the engine room into different containers makes it easier for the ship to contain the damage if there’s a fire or leak in the hull.

Cruise ship fuel tanks are also on the lower decks, but they are kept separate from the main engines.

Crew members in the engine control room on Symphony of the SeasPin

Crew members can monitor the ship’s systems from the engine control room. From the operation control center, crew members monitor the ship’s systems and act as a central area for maintaining the technical equipment on the cruise ship.

Every piece of equipment can be monitored from the engine control room to ensure the cruise ship runs smoothly.

The room is monitored 24/7 by watchkeeping teams. Each crew member is assigned specific machinery. For example, one person may be responsible for the freshwater generators and water pumps and another for the fuel oil systems.

How Big is a Cruise Ship Engine?

A crew member performing maintenance on an engine on a cruise shipPin

A cruise ship engine room spans several decks and holds the ship’s engines, fuel tanks, water systems, generators, control room, engine workshop, air conditioning, and other essential navigation systems.

Modern diesel-powered cruise ships have between four to six medium-speed (500 revolutions per minute) engines. Each engine can generate upwards of 25,000 horsepower or nearly 18.5 megawatts.

The engines on a cruise ship can be up to 45 feet long, 27 feet high, and weigh up to 275 tons.

These massive engines can propel cruise ships at an average speed of 18-22 knots.

Cruise Ship Engine Technology

Cruise ship engine technology has evolved from wind and sails to newer liquified natural gas technology.

We’ll cover some of the most popular technologies used by cruise ships.

Steam Engines

One Set of Reciprocating Engines in the Erecting Shop during the construction of the TitanicPin
One of the Titanic’s reciprocating steam engines is under construction.

When the cruise industry began in the mid-1800s, vessels were propelled by steam engines.

Steam engines had boilers that used wood for fuel. Later steam engines used coal.

The boiler produced steam which created pressure in a pressurized system. The pressure moved pistons which drove the propeller shaft.

The Titanic was powered by two huge triple-expansion steam engines and a small propeller. (Source)

Diesel Engines


Diesel engines propel most modern ships. Cruise ships may have four to six medium-speed (500 rpm) engines producing 8-10MW each.

Diesel engines work on the same concept as steam engines. Rather than steam, the ignition of diesel fuel pushes the pistons up and down, turning the crankshaft attached to the propeller shaft.

Many of today’s diesel-engine cruise ships also employ a shaft generator to generate electricity for shipboard services, like lighting.

A shaft generator converts the circular motion of the propeller shaft into electricity. However, shaft generators only operate when the ship is moving. And can’t generate electricity while docked in port.

Diesel-Electric Cruise Ship Engines

Engineers repairing a cruise ship propeller at a dry dockPin

Almost all new diesel-powered cruise ships use diesel-electric engines.

The engines work the same as a traditional diesel engine, but rather than connecting to the propeller shaft – diesel-electric engines connect directly to large generators.

A diesel-electric engine has one job, generating electricity.

The electricity produced by the engine is used to power the ship’s propellers.

These engines provide greater efficiency than traditional diesel engines.

While connected to a generator, the engines can run at their most efficient settings regardless of the travel speed. Whether the ship is sailing at 10 or 20 knots, the engines can operate a peak efficiency.

Diesel-electric engines are popular because of their ease of control, low noise, minimal vibration, and relatively compact size compared to other forms of propulsion.

Marine vessels that run on diesel power must carry exhaust-treatment systems and catalytic-reduction equipment to reduce the environmental impact of the ship.

Gas-Turbine Power System

A front-facing view of the funnel on royal caribbean's freedom of the seas with dark smoke coming out of the exhaustPin

Royal Caribbean Group was the first company to experiment with gas-turbine systems.

Compared to diesel engines, gas turbines offer several advantages, including:

  • Lower environmental impact.
  • More reliable.
  • Take up less space.
  • Gas engines require a smaller maintenance crew and less inventory.

The heat generated from the engine is recovered and used to produce electricity for other onboard systems, such as air conditioning and water heating.

Despite their advantages, gas propulsion is not widely used in the cruise industry. Gas-powered ships are faster, but most cruise ships don’t travel faster than 22-25 knots.

Diesel engines have greater fuel efficiency at slower speeds, and the high gas price compared to diesel makes them more costly to operate.

LNG Powered Ships

Carnival Mardi Gras Rendering sailing in open ocean ariel viewPin
Mardi Gras is one of the first LNG-powered cruise ships (Photo Credit: Carnival Cruise Line)

Many new cruise ships are propelled by liquified natural gas (LNG).

LNG is the cleanest fossil fuel currently produced. According to Cruise Critic, LNG-powered cruise ships can “reportedly reduce sulfur emissions by as much as 99 percent and nitrogen oxide emissions by up to 85 percent.” LNG can reduce carbon emissions by up to 20 percent.

The special engines of LNG-powered cruise ships use natural gas cooled to approximately -260°F. Once cooled, the liquid form of natural gas is about 600 times denser than natural gas, making it easier to transport.

Carnival Cruise Line announced the first LNG-powered vessels in 2015, using a “dual fuel” design. The ships can burn both liquified natural gas and marine fuel, reducing the required fuel storage space.

AIDAprima became the world’s first LNG-powered cruise ship on her debut in 2016.

Natural gas is purer, cleaner, more efficient, and cheaper than other fossil fuels. But it’s a relatively new technology, and not all ports have the facilities for refueling LNG-powered ships.

Because natural gas burns cleaner than other fossil fuels, the engines require less maintenance. But LNG has a lower fuel density than diesel, so LNG vessels need fuel tanks that are twice the size.

Emergency Generators

Every cruise ship has an emergency generator to maintain vital electrical power in case of engine failure.

The emergency generators are located away from the main engine room, usually on a higher deck. Their location isolates them from catastrophic damage in the engine room (for example, a fire).

The generators can operate critical navigation systems, emergency lights, and other vital equipment. But emergency generators can’t power the ship.

Larger ships may have multiple emergency generators. But due to the size constraints, they can’t produce the same power as the main engines and cannot propel the ship.

What happens if the generator fails?

Cruise ships have several redundant systems to ensure the safety and security of passengers. If the generators fail to work during an emergency, cruise ships have an emergency battery backup to power the most critical systems for up to 24 hours.

Shore-to-Ship Power Supply

Large cruise ships of Carnival, Norwegian and Royal Caribbean cruise lines docked in port of Nassau, Bahamas on sea water and cloudy sky backgroundPin

Despite innovations in engine technology, cruise ships produce a lot of pollution.

To further reduce ships’ environmental impact, many cruise ships can connect to the cruise port’s power grid, known as “shore-to-ship power” or “cold ironing.”

In the past, cruise ships kept their engines running while docked to generate electricity for shipwide services.

But most of the energy produced by the ship’s engines goes towards powering the propellers, and running the engines while docked created massive energy waste.

Some cruise ships used smaller generators to power the hotel and amusement functions. The smaller generators allow cruise ships to shut off the main engines in port, reducing pollution.

Modern cruise ships are equipped with systems to “plug in” to the local power grid. Even some older cruise ships are being retrofitted to allow for shore-to-ship power.

Not all cruise ports have facilities to enable shore-to-ship energy. But many larger cruise ports have dockside electrical hookups that allow cruise ships to shut off their engines and run on the city’s electrical grid. The technology reduces harmful emissions by up to 95% while ships are docked.

Considering how much time cruise ships spend docked at port, it significantly reduces sulfur and carbon emissions.

How Loud is the Engine Room of a Cruise Ship?

A crew member on a cruise ship performing maintenance on an engine while wearing hearing protectionPin

A cruise ship engine room is incredibly noisy, exceeding 173 decibels. At this noise level, the noise in an engine room can cause immediate damage to your hearing without proper ear protection.

For reference, a gunshot is 130 decibels.

Engine rooms have insulation and sound-reducing technology, so it’s not as noisy. To prevent hearing damage, crew members must wear hearing protection when entering the multi-story engine room.

But guests don’t have to be concerned about the noise.

Thanks to the insulation and sound dampening, you’ll only hear a slight “purr” if you’re near the engine room.

You may feel the engine’s vibration if your cabin is on the lower decks, near the aft. On most ships, the noise isn’t enough to cause any annoyance or trouble sleeping.

But if you’re a light sleeper, accommodations near the engine room are among the worst cabins on a cruise ship.

Where are the Fuel Tanks?

The fuel tanks are located below the passenger decks, near the engine room. The fuel is stored in double bottom tanks.

How Much Fuel Can a Cruise Ship Hold?

A large cruise ship of 1,100 feet in length can hold between 1 to 2 million gallons of fuel.

It’s enough to power the cruise ship for up to two weeks of sailing without refueling.

Are There Cabins Near the Engine Room?

Newer cruise ships have a large gap between the cruise ship engine room and passenger cabins to minimize noise and vibrations.

However, you may still find cabins reasonably close to the engine room.

If you book a cabin near the engine room, you can expect to hear some noise and feel the vibrations caused by the engines. However, cruise ships use sound-dampening technology and insulation to minimize noise pollution.

The engines are typically cheaper because most passengers avoid booking cabins next to the engine room.

Cabins near the cruise ship engine room aren’t noisy enough to cause annoyance or sleeping issues.

If anything, the vibrations caused by the engines are more likely to cause annoyance over the sound of the engine.

How Much Fuel Do Cruise Ships Use?

It takes a lot of fuel to power a cruise ship.

The average cruise ship uses around 18.3 gallons of fuel per minute or 1100 gallons per hour. (Source)

Article by

Marcello De Lio

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