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What Does SS Stand for on a Boat? (SS & Other Prefixes)

Written by Anthony Roberts / Fact checked by Jonathan Larson

what does ss stand for on a boat

Although some folks believe “SS” on a watercraft stands for “steamship,” it is no longer “accurate” in the age of nuclear reactor-driven and gas-powered vessels. So what does SS stand for on a boat in modern times? That would be a “single-screw ship.”

But that is only half the story because many boat abbreviations continue to sow confusion even among boaters. This article will enlighten you on these ship prefixes, so please continue reading.

What Does “SS” Mean?

The “SS” acronym for boat units originated in the late 18th century, coinciding with steam-powered watercraft development and widespread use. Hence, this boat acronym stands for “steamship.”

1. History and Origins


The French naval engineer and architect Marquis Claude de Jouffroy built the world’s first steam-powered paddle boat, “Pyroscaphe,” in 1783, drawing inspiration from Scotsman James Watt’s steam engines.

With the Industrial Revolution in full swing, moving goods between Albany and New York City and vice versa became more expedient because Robert Fulton’s steamboat “Clermont” now plied the route, beginning in August 1807.

Moreover, trans-Atlantic crossings became more frenetic with the introduction of these steam-powered ships.

Long story short, the 19th century saw America and Europe boom because of steam-powered boats crossing the vast ocean and traversing long and winding inland waterways.

Unsurprisingly, navigators began giving their ships SS boat names, such as SS Deutschaldn, SS Bremen, SS Home, etc. Hence, the SS ship meaning has its origins in the “steamships’ ‘ that fueled the Industrial Revolution. The phrase also differentiated the vessel from boats with a different propulsion system (i.e., paddle, sail, or oars).

2. The Modern “SS” Meaning


The Industrial Revolution also paved the way for the development of the internal combustion engine. For example, John Barber created the gas turbine in 1791, and Robert Street developed the internal combustion engine two years later.

In 1886, the German engineer Gottlieb Daimler collaborated with shipbuilder Friedrich Lurssen to create the first motorboat, “Rems.” The internal combustion engine produced 1.5 horsepower, churning out 700 RPM. It harked Lurssen Yachts’ creation, a company that exists even today.

So, why are ships called SS?


By the 18th century, the terms mostly referred to “single-screw ship,” denoting the type of propeller-driven propulsion system in internal combustion engine-powered vessels. Its counterpart is the twin-screw, which features two propellers—one on each side of the keel—and goes by the TSS prefix.

That said, some SS ships are both steam-powered and equipped with a single-screw propeller. The most notable example was the SS Archimedes—the first-ever steamship with a single-screw propeller.

Given how obsolete steamships have become in the modern age, most ship names containing the prefix SS nowadays dictate that they are single-screw vessels.

Unfortunately, few boaters and non-boating folks know SS means a “single-screw ship.” Most would still refer to these vessels in their early 18th-century definitions as “steamships.”

Common Prefixes


It is worth noting that “SS” is not the only acronym you will encounter. You can also see the following ship abbreviations prefixing a modern watercraft’s name.

  • CS – cable ship
  • FV – fishing vessel
  • MY – motorized yacht
  • TS – training ship
  • RMS – royal mail ship
  • LB – lifeboat
  • MT –motorized tanker
  • RV – research vessel
  • GTS – gas turbine ship
  • SV – sailing vessel
  • PSV – platform supply vessel
  • MS or MV – the MS ship meaning is “motor ship, while MV is “motor vessel” (not “motor vehicle”)
  • NS – nuclear ship

What Does it Mean?

Analyzing the ship naming conventions reveals that governments and boaters classify their vessels according to the origin, use (i.e., fishing, cable, mail, research, or training), and power source (i.e., nuclear or motor).

So, what does SS mean on a ship? As mentioned, we can say, with utmost conviction, this abbreviation means a “single-screw ship.” It does not matter if the vessel runs on steam, fuel, or nuclear power. If it has one propeller, it is safe to assume it is a “single-screw ship” or SS.

Other Similar Prefixes That Can Get You Confused


Although we are confident that SS means “single-screw ship,” some similar prefixes can add to the confusion.

For example, some folks use “SS” to denote a “sailing ship.” However, as noted above, most sailors now name sailboats “sailing vessels” or SV.

There is also the US Navy’s naming convention for its vessels, with warships having USS before the ship’s name. It might have the letter “U” in front of the “SS,” but it will be inaccurate to call it “United Single-Screw Ship.”

To be clear, USS stands for “United States Ship,” which is the American equivalent to the British (and its colonies) “His/Her Majesty’s Ship” or HMS.

The US Navy’s auxiliary or support vessels have a USNS (“United States Navy Ship”) to distinguish them from USN warships.


Most folks will argue the correct answer to the question, “what does SS stand for on a boat?” is “steamship.” However, we must point out that most vessels with an SS prefix nowadays do not run on steam power. Hence, the most accurate answer is “single-screw,” describing the boat’s propulsion type.

Please do not confuse SS with a “sailing ship” (we already use the term “sailing vessel” for these watercraft) or a warship of the United States Navy (that is, “United States Ship”).

Other abbreviations are more straightforward to decipher. At least you now know what SS stands for in a boat.

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