Quality Marine Products Distributor


C.W.F.Hamilton & Co.


HJ-274 designed for diesels to 350 hp @ 2800 rpm - very popular drive for commercial fisherman and tour boat operators as singles, twins, and triples with hydraulic bucket controls, maximum wt 4500 kg for singles and 10,000 for twins.

whisperjet 36 2x274

General Description

The 274 waterjet is normally directly driven by a high speed marine diesel and can be used in planing and displacement craft or in a dual speed role as both loiter and high speed boost propulsion. With it's computer aided impeller designs the 274 waterjet provides high propulsive efficiencies, at least equivalent to the best propeller systems at planing speeds of + 25 knots. Any number of jets can be employed without loss of propulsive efficiency. 

The waterjet mounts inboard at the stern, drawing water through an intake fixed to the hull bottom. The intake is protected by a highly developed screen which, at planing speeds, is largely self cleaning. An intake screen rake is optional. 

The pumping unit carries through the transom, where it is sealed with a rubber 'O'-ring seal, and discharges water directly aft through the outlet nozzle. The reaction of the water being thrust rearwards generates a powerful forward thrust which is fully transmitted through the intake base to the hull (no thrust is transmitted to the engine via the driveshaft).

Steering A steerable nozzle deflects the water to port and starboard, giving powerful steering. Steering is actuated via an inboard mounted tiller. Preferred control is by a manual hydraulic  system however, less efficient rotary cable steering is optional. 

Reverse A split duct thrust reversing deflector cuts the jetstream aft of the steering deflector, providing an infinite range of ahead, zero or astern manoeuvring speeds. Control is by a cable operated Hydraulic Servo Reverse Control (HSRX) system - a follow up system where the reverse deflector "follows" control lever movement. The HSRX system comes complete with hydraulic powerpack (JHPU) and oil cooler integral with the jet. 

Full steerage is always available regardless of reversing duct position i.e. regardless of of speed or direction. By working reverse and steering in unison a resultant thrust can be obtained in any direction giving 360 degrees manoeuvring. 

Designed and manufactured in corrosion resistant materials to international standards, 274 waterjets are further protected by fitting of sacrificial anodes. The units are supplied factory tested as a complete package including  integral steering and reverse systems with controls and powerpack. 

Installation is simplified as an aluminium intake base is supplied with each jet. This is fixed in the hull to form the correct jet inlet shape and provide a mounting for the builder to fit the jet. 
The standard 5° intake block positions the jet at 5° to the hull bottom, to allow close direct drive coupling of the engine. 
An optional 0° intake block positions the jet parallel to the hull bottom, allowing a reduced engine installation height when using a drop-center gearbox. 

The intake block welds into an aluminium hull or is moulded into GRP or wooden hulls. The GRP version eliminates the need for boat builders to mould a thick GRP block, saving both time and money. 

A gearbox is not necessary as the waterjet matches a large range of common marine engines directly driven off the engine's flywheel. The engine should be left hand rotation (anti-clockwise when looking on the engine flywheel).

Extensively tested in both HamiltonJet's Hydrodynamic Test Facility and operational vessels,  the 274 waterjet is an ideal propulsion unit for high speed work,  patrol boats, and pleasure craft where operators require proven performance and reliability.





Not all hull forms are suitable for jet propulsion. The hull shape should be optimized for the craft displacement and design speed. The following Scope of Use is only a guide to achieving best performance and it is important to seek a fully detailed application analysis from HamiltonJet before proceeding, especially if the proposed application is outside any of the limits shown.



Single Jet

Twin Jet

Triple Jet



 4 - 5 tonnes

9 - 11 tonnes

14 - 17 tonnes

Power to Weight

52 kW/tonne
(70 hp/ton)

48 kW/tonne
(65 hp/ton)

45 kW/tonne
(60 hp/ton)

Maximum Power 
Input per jet

300 kW (400 hp)


  • Above guidelines assume hull size and shape are suitable for the planned displacement.

  • Plan for a minimum cruising speed of 25 knots laden but keep in mind that the higher the boat speed, the better the propulsion efficiency achieved.

  • For speeds above 30 knots, monohedron or constant deadrise of the aft sections of the hull are recommended. This maintains directional stability and deadrise angles between 5° and 25° are typical.

  • For speeds between 25 and 30 knots, some warp in the hull lines may be acceptable, though some keeling could be required to maintain directional stability.


  • Hull resistance in this speed range can be extremely high for some craft - consult HamiltonJet in all cases 

  • Long narrow hulls are best suited, including catamarans of semi-planing or semi-displacement  design. 

  • Maximum Recommended Power Input per jet: 150 kW (200 hp)




Single Jet

Twin Jet

Triple Jet



9 tonnes

20 tonnes

30 tonnes

Maximum Power
input per jet

110 kW (150 hp)


  • a conventional vee stem bow and 5° minimum deadrise aft is recommended to avoid air entry into the the jet. 

  • Minimum jet immersion is with the waterline at the jet mainshaft.

  • For displacement hulls, speed depends more on efficient hull shape than displacement or power input.

  • Best efficiency will be obtained using low power input at, or below, the hull's natural displacement speed. 

  • The displacement guidelines shown above can be at least doubled for long, easily driven hulls.



Because engine overload does not occur and appendage drag is eliminated, model 274 waterjets are a simple solution ot multiple speed capability such as loiter and/or boost functions, whether mixed with other size waterjets or other types of propulsion systems.

Please note that dimensions above are indicative only - refer to 274 designer's manual for complete technical data. Due to HamiltonJet's policy of continuous development, all specifications are subject to change without notice or obligation. 

While Hamilton Jet provides typical data for each of its jets, however they are subject to change without notice and are provided for comparison purposes only. Hamilton Jet is very interested in the success of your installation as is Jastram Technologies. For this reason anyone considering a jet purchase is encouraged to contact Jastram in the earliest planning stages to provide boat hull and engine information so Hamilton Jet can advise the best matches for impellor to engine, and jet to boat in your application and provide preliminary performance estimates.

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last updated 30th May 2005