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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.

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.

274

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.