Choosing a power plant for an inflatable vessel is often a dilemma, especially when standard propeller motors no longer meet the owner's requirements. Many fishermen and water enthusiasts are considering installing a propeller. water-jetThis desire is driven by the specific nature of exploitation in shallow areas where the risk of damage to the screw against rocks or grass is too great.
Conversion of an outboard motor to a water jet propulsion system is a complex technical process that requires a deep understanding of hydrodynamics and mechanics. inflatable boatUnlike a metal case, it has its own features that must be considered when designing a water intake and mounting a nozzle. In this article, we will discuss all the nuances that will help you make an informed decision and avoid fatal errors during modernization.
It is important to note that the installation water-jet It is not a panacea for all evils and has both its indisputable advantages and significant disadvantages. Inflatable boat With jet drive, it becomes safer for swimming, but it loses its maximum speed and efficiency. Let's take a closer look at whether it is worth the effort in your particular case.
Advantages and disadvantages of water jet thrust on PVC
The main argument for this is the absolute safety of people in the water next to the boat, and the absence of a screw allows you to safely dock on gently grassy banks and pass areas with rocky bottoms. Water-jet engine practically not afraid of algae, which are often wound on the propeller, blocking movement.
However, the conversion of the outboard motor into a water jet version leads to a loss of efficiency. inflatable boat It gets heavier because of the weight of the water jet nozzle and the water that fills the channel, which is especially critical for low-power engines, where every kilogram of weight affects the planing.
- 🚀 Safety for swimming and animals in the water
- 🌿 Passage through overgrown and stony shallow waters
- 🛡️ No risk of winding grass on the shaft
- 📉 Reduce the maximum speed of the boat by 20-30%
⚠️ Attention: Installation of jet drive on a light PVC boat can shift the center of gravity and change the differentiation, which will require the transfer of the transom motor or cargo.
The noise of the system should also be taken into account. Water-gun installation It often emits a higher frequency hum than a regular propeller, which can be critical for those who like quiet fishing, and the vibration from the impeller is transmitted to the transom, requiring high-quality vibration insulation.
Choice of water jet nozzle for outboard motor
The market offers ready-made solutions, but often enthusiasts make them. water-jet When choosing a finished kit, you need to pay attention to the material of the case. AMG or stainless steel is preferable to plastic, which can deform when hit by a hard obstacle.
The key is that the diameter of the intake is the engine power. water-jet At 5-8 hp, the diameter of the inlet must be strictly calculated, and too narrow a channel will create excessive resistance, and too wide will not provide the necessary flow rate.
Table of power and diameter correspondence
For the engine 5 hp is optimal diameter 60-70 mm For 9.9 hp - 80-90 mm Exceeding the diameter by more than 10% of the calculated will lead to cavitation and a drop in thrust.
It's important to check the kit's completeness. water-jet There must be elements for the reverse, because changing the direction of the jet is the only way to reverse.
| Parameter | Importance for small boats | Impact on the move |
|---|---|---|
| Diameter of water intake | 60-80 mm | Determine the amount of water being pumped |
| Length of nozzle | 250-350 mm | Affects the formation of the jet |
| impeller material | Brass/Stainless steel | Resource and impact resistance |
| Weight of nozzle | 3-6 kg | Affects the stability of the boat |
When buying a finished nozzle, make sure that the kit has a flange to fasten to the lower unit of your particular motor, as the standards from different manufacturers (Yamaha, Tohatsu, Mercury) may differ.
Technical features of installation DIY
Installation water-jet The process of removing the regular propeller and the lower unit, which requires care to avoid damaging the sealing seals, starts with a inflatable boat. outboard motor It must be completely disassembled at the bottom to integrate the water intake channel.
The most difficult step is sealing the joint between the motor body and the water intake. inflatable boat It does not forgive leaks, as the water inside the lower unit can lead to water shock or corrosion. Use high-quality marine sealants on a polyurethane basis and threaded fixers.
- 🔧 Dismantling of the standard screw and anti-cavitation plate
- 🔧 Installation of the transition flange on lower unit
- 🔧 Installation of a water intake channel with a filter grid
- 🔧 Steering and reverse cable attachment
⚠️ Note: When drilling holes in the metal parts of the engine, use only cobalt-coated metal drills to avoid overheating and steel release.
Pay special attention to the cooling system. water-coat It can block the regular water intake holes to cool the engine, and you need to provide an additional bypass channel or upgrade the existing one to ensure that the engine is cooled. motor I didn't overheat at full speed.
☑️ Check before the first launch
The impact of jet drive on the driving qualities of the boat
After installation water-jet You will notice a change in the behavior of the boat. Inflatable boat It becomes more roller-like at low speeds because there's no rotor-stress, which creates a stabilizing moment, and it accelerates more smoothly, but more slowly.
Gleaming. water-jet The boat is more sensitive to roll, and if the propeller boat can burrow or take off when rolling, the jet can maintain a more predictable but inert trajectory.
Manoeuvrability is a separate topic, and the circulation radius of the jet drive is much smaller, which is a plus in narrowness, but the response to the steering wheel shift has a slight delay that you need to get used to. inflatable boat with jet drive worse holds the course in the side wind due to sailing and the absence of the underwater part of the lower unit below the keel level.
The watercraft is ideal for quiet movement in shallow water and fishing in overgrown bays, but is not designed for high-speed walks or towing a skier.
Maintenance and care of the water jet system
Operation water-jet It requires regular monitoring of the internal surfaces, salt deposits and sand can reduce the pump efficiency, and after each release to salt water, it is recommended to wash the system with fresh water.
Visual inspection of the impeller should be done every 10-15 hours, even small chips on the blades. impeller They can cause vibration and shaft beating. Water-gun nozzle It should be clean inside: any foreign objects (rags, fishing line) should be removed immediately.
Lubrication of bearings and oils is a critical procedure. Unlike a screw, where the lubricant often changes with the oil in the gearbox, in a jet drive, nodes may require individual maintenance according to the nozzle manufacturer's manual. Don't ignore the regulations to avoid jamming the shaft.
⚠️ Warning: Never run a water jet engine outside the water or with the water intake closed for longer than 10-15 seconds – this will cause instant overheating and collapse of seals.
Comparison with alternative solutions
Before deciding on the installation water-jetCompare it to other options, like using a larger pitch screw or a protective casing (fungus) can solve the grass problem, but it won't save you from stones. PVC boat With a conventional screw remains more versatile for most tasks.
If your goal is purely shallow water, you might want to consider vertical shaft electric motors, which are also safe but silent. water-jet Internal combustion remains the uncontested leader in traction in difficult conditions.
Ultimately, the choice depends on the geography of your voyages: for the Volga Delta, Siberian rivers with rolls or sea shallows. water-coat For reservoirs and lakes with clean bottoms, a traditional propeller will be more efficient and cheaper to maintain.
Cost of reworking
The average cost of a finished water jet module is from 15 000 to 40 000 rubles. Installation in a specialized service will cost another 50-70% of the cost of the equipment. Self-installation saves money, but requires skills.
FAQ: Frequently asked questions
Will the speed of the boat drop after installing the jet drive?
Yes, the average speed loss is 20 to 25 percent compared to a screw equivalent of the same power, but in overgrown areas, you can move where the screw motor will stand.
Can I make a water jet nozzle myself from the pipes?
Theoretically, you can use PVC or aluminum pipes, but it's difficult to create an efficient hydrodynamic shape. Artisanal products often have low efficiency and can collapse at speed.
Should I change the oil in the gearbox more often when using jet drive?
No, the oil change regulations in the gearbox. boat-engine remains standard, since the water jet nozzle is installed outside and does not affect the internal processes of lubrication of the gearbox.
Will the jet drive be suitable for a boat less than 3 meters long?
For boats shorter than 3 meters, installing a jet drive is impractical, and losing power and increasing weight will make the boat almost unglissable, especially with one passenger.