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Wärtsilä Midsize Waterjets

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Wärtsilä Midsize Waterjets

Wärtsilä has developed the Midsize waterjet range to provide an easy to install solution for waterjet propulsion up to 4500 kW. The inlet duct is added to the supply and delivered pre-assembled on a skid for direct 'weld-in' or 'bolt-in' connection into the hull. The shaft line of the waterjet is aligned and all waterjet components are mounted on the skid. All auxiliary systems are mounted on the skid including the piping and electrical wiring.

All midsize waterjet sizes are available in a steering/reversing (SR) or booster (B) execution. The Midsize waterjet range consists of 5 sizes starting with the LJX 510 up to the LJX 810. To reduce weight of the waterjet system, aluminium is chosen for the construction of several components. Components that play a critical role in the performance of the waterjet, like the stator bowl and the impeller, are constructed out of a high grade stainless steel like in our modular waterjet series.

    Key benefits

    • A compactly designed axial pump with excellent efficiency, cavitation, and noise characteristics.
    • The waterjet unit is completely pre-assembled, thereby reducing installation and commissioning time.
    • High performance components in stainless steel to prevent wear and corrosion.
    • The water lubricated bearing in the stator bowl provides an environmentally friendly solution.
    • Water lubricated face type stern tube seal with an optional inflatable emergency seal.
    • Inboard mounted thrust bearing block, for increased life and easy maintenance.
    • Inboard hydraulics provide an environmental friendly solution, increased life, and cost saving easy maintenance.
    • Machinery controls integrated within the unit.
    • Reduction of total costs of ownership


    The characteristics of a waterjet make it a good propulsor for numerous applications.

    • High speed vessels; waterjets have better propulsion efficiency at ship speeds over 25-30 knots.
    • Shallow draft vessels; the integrated steering function provides benefits for rescue vessels, inshore passenger ferries, landing crafts & special work boats.
    • High power density; the pressure built-up in the waterjet inlet allows small dimensions.
    • Maneuverability; waterjets have integrated steering and reversing with quick response times.

    Examples of such applications include:  

    • Fast ferries
    • Littoral combat ships
    • Fast patrol boats
    • Rescue vessels
    • Fast yachts
    • Fast supply vessels and workboats
    • Landing craft

    Technical info

    Weight & dimensions table
    Size A
    Weight steering
    510 1540 1065 2350 2975 1100 510 1400 1050 450
    570 1730 1190 2520 3325 1200 570 1750 1300 600
    640 1930 1335 2720 3735 1400 640 2400 1800 850
    720 2170 1500 3000 4200 1400 720 2850 2250 1250
    810 2440 1690 3220 4725 1400 810 3600 3000 1750
    Inboard length may vary depending on the optimized shape of the inlet duct
    Midsize WJ Technical info

    Downloads and links

    We are constantly improving our midsize waterjets portfolio and our offerings focussing on the highest possible efficiency with lowest weight and reduced cost of operation. All to achieve the best product solution for our dear customers.

    Sander van Oosterhout, Product Director Waterjets, Wärtsilä

    Waterjet size selection

    The graphs indicate the jet size required based on the relation between the engine power and the design speed of the vessel. For instance, a ship with four 1250 kW engines and a corresponding vessel speed of 33 knots will need four 510 midsize waterjets. A ship with a design speed of 40 knots at 1250 kW power can use 450 size waterjets. The correct jet size is thus indicated by the line above the intersection of the power and the corresponding vessel speed.

    Please contact our global waterjets team for an optimized jet selection based on specific vessel design parameters and operating profile, or for details on waterjets above 50 knots or 30 000 kW. DXF/DWG format general arrangement drawings of the most often used sizes are available.

    Midsize waterjet selection


    Our waterjet customers and operators around the globe are looking for a high-quality and reliable solution, while shipbuilders come to us for ease of integration and competitive pricing – our midsize waterjets meet these and many other needs.

    David van Luijtelaar, Global Sales Manager Waterjets, Wärtsilä
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