The world’s largest cruise ships run on engines so huge they weigh over 240 tons each

Cruise ships aren’t just floating hotels; they’re more like floating cities drifting across the ocean – and Royal Caribbean’s ‘Icon of the Seas’ is no exception.

And to keep a city this size moving, you need more than batteries and good vibes.

Beneath the pools, water slides, and all-you-can-eat buffets sit machines so massive they make apartment blocks look small.

Think of a bus. Now make it 10 times heavier. Then multiply by six. That’s what’s hiding in the bellies of the biggest cruise ships in the world.

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Engines on cruise ships are pretty huge

Take Royal Caribbean’s ‘Icon of the Seas’ – currently the biggest cruise ship on Earth. 

It stretches 1,197 feet, weighs 248,663 gross tonnes, and carries 7,600 passengers plus 2,350 crew. 

That basically makes it a small town on water.

To push that mass forward, it relies on six Wärtsilä engines: three 14-cylinder and three 12-cylinder. 

The ‘smaller’ 12-cylinder tips the scales at 203 tons, measuring 34 feet long, 15 feet wide, and 12 feet tall. 

The 14-cylinder? A whopping 245 tons and nearly 40 feet long. 

That’s more floor space than some downtown apartments.

And wanna know something wild?

‘Icon of the Seas’ doesn’t even use Wärtsilä’s biggest option. 

That honor goes to the 16-cylinder, which stretches 41 feet, weighs 259 tons, and punches out 24,500 horsepower. 

Then there’s Caterpillar’s rival MaK 16-cylinder, which is even more of a monster.

It measures 47 feet long, almost 22 feet tall, 240 tons, and is good for 20,710 horsepower. 

Ships like ‘Costa Toscana’ and ‘Costa Smeralda’ run four of those each.

But engines aren’t everything. 

On ‘Icon of the Seas’, the six giant diesels act like power plants, feeding electricity to Azipod thrusters outside the hull. 

Each of these pods weighs over 200 tons and carries a 20-foot propeller, cranking out 20 megawatts – about 27,000 horsepower. 

And because they can spin a full 360 degrees, they handle both propulsion and steering. 

Engines this big don’t come clean

All that muscle comes at a cost, and it’s measured in fuel bills that could bankrupt small countries. 

Estimates online suggest ‘Icon of the Seas’ burns about 4,000 gallons an hour – nearly 100,000 a day.

That kind of burn rate explains why a 2017 study found cruise fleets pumping out more sulfur oxides around Europe than all the cars on the continent. 

To curb that impact, new flagships like Icon are turning to LNG  (liquefied natural gas). 

LNG eliminates sulfur and cuts carbon by 70 percent… but also loses small amounts of methane in the process.

So while progress is being made, it’s still not quite climate-friendly.

These engines remain engineering miracles. Steel giants moving floating cities. 

But the bigger the ships get, the more complex the question: can cruising ever truly go green?

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