About Twin Disc Water Jets
On February 96, Twin Disc Incorporated signed a licensing
agreement with Doen Marine PTY Ltd of Melbourne AUSTRALIA to
manufacture and market Doen’s line of water jets.
Doen Marine of Australia are among the pioneers of water jet
propulsion. For more than 25 years they have been designing and
manufacturing water jet units for use throughout the world.
The current product range is comprised of more than fifteen model
sizes and caters for engines from 30 Hp up to 2000Hp marine diesels.
Thanks to the agreement Doen Jets will be manufactured by Twin
Disc and distributed throughout its extensive worldwide distribution
Head office for European Middle Eastern and African markets has
been established in Capezzano Pianore(LU) Italy.
Please send all the inquires concerning water jet propulsion
systems to the following address:
TWIN DISC srl
MARINE PROPULSION DIVISION
Zona Industriale Le Bocchette, 92
55040 Capezzano Pianore(LU) Italy
Phone +39 0584 969696
Fax +39 0584 969692
E-mail : firstname.lastname@example.org
WATER JET PROPULSION SYSTEMS
Written reference is made to water jet propulsion as far back as
the 17Th Century. In fact in this period there are two patents
granted that suggest the use of a jet of water to propel ships.
The theory of water jet propulsion was subsequently investigated
and discussed by Frenchman Daniel Bernoulli in 1753. Bernoulli
suggested that a stream of water could be used to propel a boat and
conducted some experimentation to confirm the principle of water jet
While the theory may have existed we did not see practical
examples until the mid twentieth century when there was the
technology and sufficient understanding of the system.
A water jet system works in the same way that rockets, jet
airplanes do. It is Newton’s third law, “for every action there
is an equal and opposite re-action”, that simply explain the
phenomenon. A jet of water is expelled from the rear of the boat.
The reaction of this action is to propel the boat forward.
The water jet itself (the propulsor) is essentially a water pump.
This pump is consequently mounted into the vessel with an intake
opening flush with the hull bottom ad a discharge nozzle exiting
through the transom (back) of the hull. The pump is driven by
conventional petro or diesel engines with some very large horsepower
water jets even using gas turbine.
Some misunderstandings that people commonly have is that the exit
jet must strike the water or that the thrust will be greater if the
water jet strikes the water. This is most definitely not the case
and the essel would be propelled even if the water jet exited into
Water jet systems are generally regarded as non conventional,
used in high speed application (+25 Knots), but the fact of the
matter is that, if correctly selected and installed, they can and do
provide a visible alternative to the conventional propeller and can
achieve overall efficiencies that are better than conventional