High-performance waterjets

Modular and midsize waterjets for ships of any size

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Waterjets and marine jet propulsion

When deciding on the right waterjet solution there are many variables to consider – from size, weight and power to efficiency, reliability, support and ease of integration. But this doesn’t mean that choosing a waterjet has to be a complicated process. With over four decades of experience in waterjet technology, Wärtsilä can help you identify the right solution for your application. 

How does waterjet propulsion work?

A waterjet generates propulsive thrust by sucking water into a pump unit through an intake/inlet located on the bottom of the vessel, then forcing the water out through the impeller, propelling the vessel forward. As the water exits the impeller it is pushed through the steering unit, which is comprised of two main components: a steering nozzle for port and starboard movements, and a reversing bucket for forward and reverse movements. This method of steering makes waterjet-powered vessels highly manoeuvrable.

The benefits of waterjets

Waterjet-driven vessels can rotate on their own axis, manoeuvre easily from side to side and perform j-turn manoeuvres as well as crash stops, sometimes referred to as bucket stops. By using water as the source of power, several traditional propulsion ‘problems’ are solved. Waterjets can operate in shallow draft conditions and are more efficient at high speeds. Since there is no equipment below the vessel, waterjet-driven vessels are also safer for swimmers and marine life.

Waterjets vs. propellers

Waterjet propulsion is often chosen instead of conventional propellers for vessels that require high speeds with low noise and vibration. For speeds above 25 knots, waterjets can be more efficient than conventional propellers. Waterjet propulsion also offers the additional benefits of improved manoeuvrability at all speeds and a significant reduction in the ship’s draught.

Types of waterjets

Wärtsilä waterjet solutions are the result of consistent innovation and development over four decades. They offer high-quality construction and proven performance thanks to their axial-pump design. The axial-pump structure is lightweight, requires less space on the vessel’s transom and increases cavitation margins for better operational flexibility. In addition, the hydraulics can be installed inside the vessel, making them easier to maintain and repair.

3D rendering of a Wärtsilä Modular waterjet

Modular waterjets

Wärtsilä modular waterjets are fully optimised according to your vessel type and power source, with a high level of customisation options available. Modular waterjets are constructed in 100% duplex stainless steel for outstanding durability.

3D rendering of a Wärtsilä Midsize waterjet

Midsize waterjets

Wärtsilä midsize waterjets are designed for 1,000–4,500 kW input powers and are delivered in five standard sizes with proven designs that offer shorter lead times and reduced costs. To reduce weight onboard, some parts are constructed from casted aluminium; critical components are constructed from high-grade stainless steel.

Applications of waterjets

Wärtsilä’s waterjets are known for their unbeatable efficiency and reliability, making them the propulsion method of choice for everything from navy and coastguard vessels, crew boats and high-speed passenger and RoPax ferries. 

Waterjet performance, technology and innovation

Wärtsilä’s state-of-the-art WXJ waterjets deliver high propulsion efficiency and outstanding performance. They feature the latest generation WXJ axial flow pump design that improves thrust by up to three percent compared to previous generation pumps, improving fuel economy and helping to reduce emissions.

Because the waterjet thrust bearing is not within the water flow inside the jet, there is no risk of oil leakage into the water. This makes them safer for the environment. Because the cavitation margins are larger, WXJ waterjets are also quieter. This is another way in which they are more environmentally friendly.

Wärtsilä WXJ waterjet series

Ever wanted to see how a waterjet works? Watch this animation featuring the Wärtsilä WXJ modular waterjet, with cutaways that pull you right into the heart of the action.

Installing lightweight, modular waterjets will reduce emissions

Wärtsilä’s modular WXJ waterjets lightweight and have high propulsion efficiency and an improved axial pump design that improves vessel fuel economy. They are a great way to reduce emissions. You will find 49 more ways in a fascinating eBook “50 great ways the maritime industry could cut its greenhouse gas emissions”. Learn more:

Download the eBook now!

Customer stories

Discover the benefits others have already gained from Wärtsilä waterjets.

  • Hales Trophy
    Wärtsilä powered Incat catamarans

    For thirty years, the Hales Trophy for the fastest Atlantic crossing by a commercial passenger vessel has been held by catamarans built by Australian shipbuilder Incat Tasmania. In fact, three successive world records for the ‘Blue Riband’ crossing have been won by Incat catamarans, and all have been powered by Wärtsilä waterjets.

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  • Balearia-slide
    High-speed catamaran for Baleària

    The largest LNG-fuelled high-speed catamaran

  • SAINT-JOHN-PAUL-II-1138-420
    Saint John Paul II

    The largest high-speed catamaran operating in the Mediterranean Sea

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  • FRANCISCO-1138-420

    The world´s fastest high speed ferry to utilize liquefied natural gas (LNG) as fuel

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  • Molslinjen-ferry-1138-420
    Express 4

    High-speed RoPax with a compact axial flow jet solution

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  • lcs2-independance-slide
    USS Independence

    The USS Independence (LCS 2) entered service in 2010 as the first of a series of initially ten. The vessel design is based on that of a high-speed trimaran and is capable of speeds in excess of 40 knots. This innovative combat ship is equipped with Wärtsilä Waterjets.

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  • spearhead-1-slide
    USNS Spearhead

    The USNS Spearhead is the first of the ten Joint High Speed Vessel (JHSV) supporting the US Navy, Marine Corps, and Army with the intra-theatre manoeuvres of personnel, supplies and equipment. It is equipped with Wärtsilä waterjets and designed to reach 43 knots without payload.

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  • navy-southafricannavy-copyrightblohm-vossgmbh-mekoa200-slide
    SAS Amatola

    The SAS Amatola, commissioned in 2006, is the first of four South African Valour class frigates. These vessels have a ‘Waterjet and a Refined Propeller’ or WARP propulsion solution with three shaft lines. (photo courtesy of Blohm+Voss GmbH)

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  • Natchan Rera
    Natchan Rera

    The Natchan Rera started service in 2007. Engine power from the vessel is converted to thrust using a newly designed waterjet, the LJX 1500 SRI, from Wärtsilä. The vessel sails at loaded speeds of approximately 40 knots. (photo courtesy of INCAT)

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  • hsv-2-slide
    HSV2 Swift

    Wärtsilä Jetguard Seals for high speed navy catamaran

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