Water jet propulsion for boats and boats: reviews of manufacturers, advantages and disadvantages

As a rule, people who decide to tie up a kind of activity (be it a hobby or a profession) with water bodies like rivers or lakes, sooner or later face the problem of choosing a boat and the type of propulsion for it. Motor-water or still screw? Each has its own pros and cons. How to choose the right thing to pay attention to? And is it worth making a choice between a water jet and a classic motor with an open propeller?

Waterjet propellers

A water-jet called an engine that provides the movement of the vessel with the help of a force created by the ejection of a water jet.

The propeller consists of a screw with a shaft (impeller), a water tube, a straightening device and a steering device.

The principle of operation consists in the flow of water through the impeller into the water intake compartment, and after the liquid is ejected through the conical tube, the outlet opening of which is smaller in diameter than the inlet one. Thus, a jet is created to ensure the motion of the motor boat. With the help of the steering device, the direction of the jet is changed by turning the propeller in a horizontal plane, which ensures the ship's turns, and the overlap of the outlet creates a reverse flow, providing the boat with a reverse.

The choice of water jets is usually inclined to people who often have to overcome littered or rapids. A conventional screw motor under these conditions risks becoming unusable due to the high risk of winding tines on a screw in shallow water or the usual ingress of large debris. In such situations, water-jet propellers are indispensable, providing high speed, maneuverability and safety.

Do not confine yourself to the opinions of participants in various forums. After all, to make a complete picture does not allow any review. The water-jet is not only a fairly complex structure, it can not be suitable for any model of the vessel. If the beginner is happy with the very idea of using a vessel with a water jet, you should stop at the ready version of the vessel with water jet in the factory equipment. And it is desirable to choose the manufacturer, engaged in the production of these engines for a long time.

Advantages and disadvantages

The design of the water-jet is especially important in that all the most important moving parts are "hidden" inside the hull. If the boat strands, the bottom touches the hull of the vessel. This feature of the design allows you to protect parts from damage, which can not be said for outboard motors with a "bare" screw. The water engine is not afraid of meeting with underwater debris.

When moving a motor boat in shallow water with a depth approximately equal to the landing of the hull (about 20 centimeters), water can overcome littered areas, as well as places with protruding water obstacles, due to its maneuverability.

If you fly on the obstacle at a depth of about 30 centimeters, the blow will take over the bottom of the boat, and not water, since the propulsion unit has no protruding parts, which is not to say about the outboard engine, where the blades assume the blades of the propeller.

Sometimes, water jet propellers are also used on recreational crafts because of the mild operation of power transmission (transmission) and lack of vibration.

Among the advantages is also the lack of additional resistance to water, typical of engines with an open propeller (propeller blades and create additional resistance). In addition, high rates of inertia, more convenient handling at high speed (both at the forward and backward speeds) are distinguished. Of no small importance is the low noise range: the suspended water jet works noticeably quieter than the motor with the propeller.

Nevertheless, it should be noted the negative side: when driving in shallow water there is a big risk that stones, sand and debris from the bottom will be drawn into the engine, because the water works according to the principle of the pump pump. This can lead to damage to the impeller, failure of the cooling system and improper operation of the drainage nozzle.

Another negative side is friction. It is caused by the high speed of movement of water inside the pipe. Do not forget about the cost of installation. The water-powered boat motors are approximately twice as expensive as conventional outboard motors with an open screw. Because of this boat with a water jet engine in the kit is significantly added to its value and perceived by customers as a whim or inadmissible luxury.

Unusual for fans of classic screw motors is the water management system. The problem is related to the fact that the classic propeller with an open propeller has a single-lever control system. Vodomotnye propellers also have a multi-link reverse-steering device. Some manufacturers manage to produce boats with an integrated water-jet with a single-lever control system. On the one hand, it helps to master the water, on the other hand, it leads to more trouble than benefits:

• First, the beginner has a wrong idea about the work of the water-jet propeller. This is due to the lack of a gearbox, which allows you to translate the gearshift lever into a neutral position. The transmission can either turn on the clutch or turn it off. The water-jet propulsor gains speed smoothly when turning on, an instantaneous reaction in the form of a jerk from the spot is not expected.
• Secondly, for a better understanding of the principles of work of the water-jet, it is recommended to pass the appropriate training course. The whole trick of controlling the water jet is to use the gas lever (to increase the speed of movement) only in an open reservoir. When moving along rapids, it is better not to do so.
• The third important minus characteristic of any type of water transport is overgrowth. This problem is especially acute with the waterbody, as all moving parts are inside. With constant use of the propeller, problems do not arise. However, if the boat is not used for a long time, the insides become overgrown. In particular, the fouling of the interiors of the sewerage system leads to a decrease in the speed of movement up to 10%. The problem is solved by disassembling the water jet and cleaning by hand, but if the motor boat has been idle for a very long time, you will have to go to the workshop and look for suitable spare parts for boat motors. Using a special color composition will solve this problem, but for a short while: a constant movement of water will quickly wash off this paint.

Watermelons - it's safe!

Of course, the safety of the water-jet engine is the main positive feature. Since the impeller is inside, the water does not pose a danger to the person staying in the water. Such devices are used on hydrocycles and boats when towing water divers and surfers.

Features of the structure of the water jet propulsion allow the motor boat to make turns almost in place thanks to the reversing-steering device (RRU), which provides a change in direction (reverse) of the outflow.

Spare parts of the water jet are easily accessible, and repairs do not cause any special difficulties. If the water jet engine has failed, you should use the services of any workshop, where it can easily be repaired or replaced with a new one. Everything will depend on the degree of damage. It may be necessary to refine the fixing, cooling and exhaust system in case of replacement.

The water jet propulsion has a number of nuances, which should not be forgotten. One of those: you should maneuver at high speeds, you should not drop those before the end of the maneuver, whether it be a turn, a turn or a reverse.

Like the outboard motor, the water jet propeller is at risk of winding algae onto the impeller, which, in turn, can jam. To prevent damage to the engine in the case of winding algae on the shaft, a special key is provided, which can be cut. It is also easy to get rid of algae by opening the hatch. Provides protection against hitting stones - grating.

How to choose water jet

Conventional outboard engines with an open propeller have an efficiency factor of 0.65-0.75 when driving at moderate speeds. For water jet efficiency is about 0.55 at a speed of 40-55 km / h. With an increase in speed to 100 km / h is already 0.60-0.65. Competent design of all elements of water jet propellers gives an efficiency of about 0.70. In this case, it is necessary to consider not only water, but also acceleration of the boat with the installed water-jet structure.

It is recommended to study a number of rules that allow you to competently select water jets, the main focus in which concerns design and manufacturing technology. It should be noted that it is necessary to pay attention to the shape of the nozzle. The drainage system must have a circular or ellipsoidal sectional shape. Less desirable options are square water pipes and in the form of a rectangle with rounded corners.

An important aspect is the angle of inclination of the water intake axis. Choose should be based on the principle "speed higher - a slope less." Water-jet boats develop a speed of 55-65 km / h, which is achieved by using a 35-39 degree angle. To achieve higher speeds, the angle should be reduced to 25 degrees. In this case, the angle of inclination of the axis of the propeller shaft is selected in the range from zero to five degrees.

Installation

Install the water-jet engine should be on light high-speed vessels, called "gliding". Such boats are designed for speeds over 60 km / h. However, sometimes water is installed and on medium-sized motor boats with an angle of inclination of the bottom (deadlift) from 10 to 30 degrees.

At installation it is necessary to consider and weight of a propulsor, after all constantly located in water adds a considerable share of weight to a vessel. Therefore, when dealing with the calculations of the vessel's "fluidity", it is necessary to take into account this important nuance. But if you look at the picture completely, the installed waterbody on the boat is a more compact version than the engine with the corner column. The additional weight is easily compensated for by the lack of a gearbox, which is replaced by a reverse-steering mechanism. It should be noted, experts recommend the installation of a special coupling between the engine and water. Thus, the isolated operation of the motor is ensured, regardless of the operating mode of the water jet propulsion unit.

Relevance

A genuine interest in water jet propulsion from commercial organizations arose relatively recently. Thanks to the experiments of shipbuilding companies in the form of installing water chutes for high-speed sea ferries, military and commercial vessels, this type of ship's propulsion has gained popularity.

Successful operational experience has shown a lot of hidden advantages, in addition to the obvious superiority, which won waterproof boats in shallow water.

For example, one of the Italian shipbuilding companies advertising a yacht with a water jet indicates such features as a high degree of adaptability to changes in load on the ship (which can very often change), as well as more significant efficiency at speeds from 60 to 95 km / h .

Water outside of shallow water

These characteristics play a significant role for a high-speed yacht, since on a classic propeller with an open propeller the ship's speed directly depends on the rotational speed of the propellers. Changing the weather conditions, contributing to slowing the course of the vessel, leads to the difficulty of maintaining a constant speed. This negatively affects the performance of the engine because it is impossible to develop a greater number of revolutions. Due to the peculiarity of the water jet, which is impossible to overload the engine, it became possible to develop a large number of revolutions, regardless of the speed of the vessel. That is, the number of revolutions does not fall, the load on the engine will remain the same, the fuel consumption per unit of time will remain unchanged, but fuel consumption per unit of time will increase.

In addition, maneuverability of water jet propellers allows yachts to moor in close river berths, rather than specialized ports. In addition, an important aspect, thanks to which water jets have won recognition in the sphere of application on cruise yachts, is their noiselessness.

Motor yachts begin to experience difficulties when driving over 50 km / h in the open sea. This is due to the increasing resistance of the water to the blade (even rotating) of the propeller. With the use of a water-resistance, the resistance is practically zero due to the design of the propulsion device, which ensures a constant flow around the body.

Cruise yachts rarely go at high speed, the need for waterjet applications is caused more by the desire for rational and safe operation of the engine. But there are also instances that increase the speed of movement in the open sea due to the power - that is, the installation of several engines.

Market share

The reliability of water chutes in littered reservoirs does not cause any complaints. It is known that ships overcome such contaminated places as the English Channel, without a single breakdown.

Despite its usefulness, water jet propulsion devices are used in diametrically opposite spheres of shipbuilding: either on multi-engine cruise yachts, or on small high-speed boats or water motorcycles. And for the latter, water is the only possible option. The lion's share of the market is made up of boats of different sizes with classic propellers. About an extremely small number of boats that go off the assembly line, having a built-in water, it is not worth mentioning.

Totally about 11% (according to experts) of the market belongs to water-jet propulsors. But this figure can significantly decrease if we consider not completely the market of propulsion devices, excluding water motorcycles, where water is an integral part of the design.

According to the forecasts of the companies that produce engines, there is a possibility of an increase of this figure to 45% due to the opening of the market potential of water-jet propulsors.

Reviews of motors and manufacturers

A lot of fishing enthusiasts prefer to use the boats "Rotan 240M" in conjunction with a water jet Yamaha 40.

According to their opinions, claims to the manufacturer of Yamaha are very small. Basically, they are connected with mistakes "with unaccustomed", because the reviews are composed mostly of those who recently changed the water from one to another. That does not immediately jerk off the spot after a smooth feed of the lever, then deeply fails the rear of the boat.

Negative feedback is seen in the address of Tohatsu. Firstly, fishermen complain about the frequent purchase of defective products. Secondly, the model Tohatsu 40 received the nickname "dishonest forties", as the engine does not give out 40 horsepower. Often replaced with Tohatsu 50, but this model quickly overheats.

Feasibility of using a propeller

The installation of a classic suspension propulsion device is advisable if it is necessary to use the simplest design and movement over water areas with a depth greater than the average at low speeds (up to 50 km / h).

Yamaha motors are well proven. There are three main types:

• Blade propeller with a medium exhaust. The peculiarity of the structure is that the outlet, through which the fuel is released, as well as the release of the energy of combustion, is located in the middle - in the center of the axis, on which the blades are attached.
• Screw constructions with an arrangement of an exhaust aperture over an axis.
• Systems with two exhaust ports located above and below the axis.

Conclusion

In general, waterproof boat motors bring a lot of advantages to the design of the boat, but the drawbacks described above should not be discounted. Otherwise, an expensive propeller can become a burden.

Foreign manufacturers produce boat water jet with very high efficiency and relatively small dimensions. For example, Yamaha water jet with dimensions of 350x560x300 mm and weighing 19 kg has a cost of about 75,000 rubles in the domestic market.

Mercury ME JET 25 ml (manufactured in the USA) is more bulky: it has a length on the upper part of the body (horizontally) 508 mm, weight about 60 kg, engine volume 420 cm ³ , impeller speed per minute reaches 5000, fully manual control. The cost in the domestic market is already 263 500 rubles.

Japanese water Tohatsu M25JET with similar characteristics (it differs only in the number of revolutions: 5200-5600 per minute) costs 287 500 rubles.

For comparison, a classic screw motor can be found at a price of 30,000 rubles and above.

Not surprisingly, because of this difference in value, a few decide to purchase water. The price is considerable, and not everyone can afford such a chic. It remains to be hoped that with time the price policy stabilizes, as foreign producers predict. Then, the water jet propelled themselves to a significant market share.

It should also be noted that the increasing popularity of the use of water chambers is ensured by the well-known manufacturers. The most famous companies are:

• Yamaha (Japan);
• Suzuki (Japan);
• Tohatsu (Japan);
• Honda (Japan);
• Mercury (USA);

The products of each company are characterized by their high quality, equipment and performance ratio.

The question of the need to obtain spare parts for boat motors is not rising sharply. It's all about the fame of the brands mentioned. Details are available both for purchase under the order, and for sale in specialized stores or car repair shops. Repair of water jets is not a big problem.

Manufacturers devote an enormous amount of time checking each drawing, detail, and each numerical value before putting the model on stream. Samples are being improved: water jets with a large number of cylinders are produced, with a large number of screws, with shafts of left and right rotation. Special attention is also paid to noise-insulating materials in the manufacture of appropriate gaskets in order not only to muffle the sound of the engine running, but also to reduce vibration. Exclusive steering systems are provided for installation in a complete set with water jet. Devices that reduce the so-called torque, in order to make the control of the vessel the most comfortable.

There are samples with a fully lever control, not involving the use of a cable system, which significantly reduces the likelihood of unpleasant situations that can suddenly bring a broken cable.

Considering all of the above, the selection of a water-meter should be treated very carefully. A lot of money invested in the acquisition should pay off in the future, and the difference between the use of screw and water jet engines should be palpable.