Vessel Hydraulic Power Systems

Hydraulic Outboard Propulsion Units

deck-mounted or transom-mounted hydraulic propulsion units. National models range from 35 to 1,000 HP. They feature steering through 180° and proportional propeller speed control in forward and reverse, providing omnidirectional thrust capability. Hydraulic power kick-up and propeller depth adjustment are available. Matched to application from stock components.

The outboard drive assembly includes the steering actuator, drive and stem rotation mechanisms, outboard stem, propeller hydraulic motor, propeller, and the outboard tilt mechanism. Routine servicing of the outdrive does not require disassembly of the unit.


Engineering, Designing And Manufacturing

Hydraulic Efficiency

“Hydraulic efficiency” is a term alluding similar sentiments to “exact estimate” or “scientific belief.” It’s not that hydraulic efficiency is an oxymoron, per se, but these aren’t traditionally two words that make sense shoulder to shoulder. If efficiency was your top benefit on the list of machine requirements, fluid power wouldn’t have been on your short list of options, at least in the past half-century or longer.

Efficiency is a word now more commonly familiar to us, thanks to the escalation of green values—especially those defining the way we use natural resources. No longer can we take a limitless and inexpensive source of energy for granted, nor can we abuse the dirty sources of inexpensive energy at the expense of our precious environment. We must take full advantage of our energy resources to achieve the work required for maintaining our standard of living, while reducing associated waste along the way.

Pivot Points

Pivot points are incorporated in the outboard drive to allow elevation of the stem for inspection or maintenance. Elevation (tilt) is accomplished without disconnecting the outboard drive from the main power source so that operational control may be returned immediately and to permit maintenance and repair without employing divers or dry-docking the vessel.

Steering System

Each propulsion unit is equipped with electric over hydraulic steering, with a hydraulic steering actuator interconnected with a drive and rotation mechanism powered by the steering and tilt hydraulic pump. The unit steers 180 degrees, port to starboard, while subjected to full propeller thrust, facilitating the vessel's ability to maneuver nearly independent of wind and wave excitation forces.

Hydraulic Propulsion Motor

The hydraulic propulsion motor is a bi-directional, variable-speed motor directly driving the propeller shaft. The hydraulic motor is installed inside the fabricated steel lower outdrive housing. The propeller shaft is supported by large, oil-lubricated taper roller bearings. The motor produces the required propeller rotative speed and is capable of complete direction reversal at full speed and torque in less than five (5) seconds. Propeller speed can be infinitely controlled in both forward and reverse directions providing excellent maneuvering ability and performance equivalent to controllable pitch propellers. Pressure limiters and cross reliefs protect the hydraulic transmission in the event of propeller blockage. The propeller can be stalled at any time without causing damage to the transmission.

Steering a commercial boat or large yacht can be similar to driving a heavy car with bad brakes. It’s difficult to stop, and response to the rudder is slow. This poses no problem in the open sea, but it can be real challenge to maneuver the vessel in a congested marina or when docking. This is where a bow thruster comes in.

A bow thruster consists of an open-ended tube that runs through the underwater sections of the hull near the bow and perpendicular to the keel. A propeller mounted at some point inside this tube can rotate in either direction. The helmsman selects the rotational direction and actuates the propeller.  As a result, the bow thruster sucks a solid stream of water in one end of the tube and forces it out of the other, pushing the bow sideways and augmenting the rudder to make steering more responsive.


The combined Research and Development expertise within our group comprises enormous potential to shape the future of waterjet propulsion. Yet at the same time we use these skills to constantly refine our existing product lines. In recent years we have accomplished this by focusing on improving waterjet serviceability and by enhancing performance with better cavitation margins and higher thrust. Inspired by latest hydraulic and electromagnetic technologys.

For instance our floating and comparatively flexible drive-shaft allows minimum blade-tip clearance and its own simple and efficient shaft seal. The mixed-flow pump was selected to give greater thrust, and our units produce higher top speeds for equivalent outputs, and lower fuel consumption during operation.

Each new waterjet design concept is developed in a 3D CAD environment. Then, scale models are built and tested by skilled Marine Engineers and Naval Architecture. When the time comes to produce crucial new parts and components, we can manufacture these in our own facilities – from casting and machining to final assembly.

Hybrid System

Reverse-reduction gear- box with controllable PTO/ PTI, hydraulically operated clutches, electric motor, elastic couplings and frequency converter.

Reverse-reduction gear- box with controllable PTO/ PTI, hydraulically operated clutches, electric motor, elastic couplings and frequency converter.

Marine Hybrid System

The hybrid system enables you to sail at normal cruising speed with a traditional Diesel engine as well as allowing you to sail in protected areas with zero emissions and in ports or marinas where silence and reduced pollution are well appreciated. During inshore navigation the silent propulsion enhances enjoyment of the landscape and, when anchored, there is no need to keep the engine running to use on-board facilities, thus avoiding disturbing the calm of the surroundings.


Hybrid navigation allows you to different uses: in the Electric mode you can sail at low speeds without emissions, while navigating on Diesel engine mode you can fully exploit the power of the combustion  engine. And you can decide whether or not to insert the battery recharge mode by simply pushing a button on the control panel.  The Booster option adds electric motor power output to the combustion engine power output and not only when on full power but also in intermediate power output where it is possible to get the best out of the rotation speed of the Diesel engine while using the electric motor only for small accelerations or changes in speed.

We offer the SAE4 bell coupling inlets and outlets; the maximum input torque (Tkn) is 560 Nm (414 lb-ft), the maximum input power is 145 kW (187 hp)  with a maximum speed of 3000 rpm and overall weight of 221 kg (487 lb).

It can be installed on new boats or retro-fitted to on-the-water boats; in this way you can have a modern and eco-friendly boat without having to replace it. Furthermore, this type of solution fits well whenever comfort is important but high speeds are not needed, such as non- displacement or semi-planing pleasure boats, passenger and freight boats, tourist river boats, charter boats, fishing boats and rescue boats. This solution will become more and more necessary to be able to navigate in  protected waters or to navigate while ensuring the protection of the environment.

The system is so compact it can be used on multiple applications and fitted in different ways. It is so flexible that it makes the boat unique in its kind, ensures a considerably reduced fuel consumption of no less than 15% while navigating on combustion engine power without causing acoustic and atmospheric pollution.


The management system MPCB is a device developed by National, both in the hardware and software, able to manage the different functionalities (modes) of the hybrid system: Diesel, Electric, Booster and Generation, as well as integrating the information of other components and supervising the overall diagnostic system.