Choosing a power plant for an inflatable vessel is a fundamental step, on which not only the comfort of movement on the water depends, but also your personal safety. outboard motor It turns a simple inflatable structure into a complete vehicle that can travel long distances and fight the wind, but the market is oversupplied, and it's easy for a beginner to get confused about the specifications, brands and types of engines.
Many factors must be considered when making a decision, from the carrying capacity of the boat itself to operating conditions, whether it is a calm lake or a stormy river with a strong current. An improperly selected unit can not only fail to unlock the potential of the boat, but also cause an emergency or premature failure of the transom. In this article, we will discuss the key aspects of the selection and use of outboard motors for inflatable vessels.
The efficiency of the propeller group depends on the engine power matching the data-sheet figures of the boat. Ignoring the recommendations of the boat manufacturer, especially regarding the maximum permissible power, can lead to the rupture of cylinders or tipping over. Competent approach to choosing will allow you to enjoy water walks for many years.
Engine types: two-stroke vs four-stroke
The first and perhaps most important question is the choice between two-stroke and four-stroke These two types are fundamentally different in design, operating principle and maintenance requirements. Two-stroke engines They are traditionally lighter, easier to build and generally cheaper to buy, and they are not afraid of long downtime and can be stored in any position that is convenient for transport in the trunk of a passenger car.
On the other hand, four-stroke They're famous for their efficiency, low noise, and no need to mix oil with gasoline, and they provide more stable traction at low rpm, which is critical for trolling, but they're much heavier, and they can only be transported in a very specific position to avoid oil leaking into the cylinder.
For small-to-medium-sized inflatable boats, where every kilogram of weight on the transom affects differentiation, two-stroke boats are often chosen, and four-stroke boats become the standard for heavy inflatable catamarans or long-length PVC boats, where autonomy and comfort are important.
- ⚓ Two-stroke engines: easy start, less weight, the need to mix fuel with oil.
- ⚓ Four-stroke engines: quiet operation, fuel economy, heavy weight and dimensions.
- ⚓ Resource of work: four-stroke engines usually last longer thanks to a better lubrication system.
⚠️ Attention: Never attempt to store or transport a four-stroke motor with a roll of more than 15 degrees without first draining the oil, otherwise you risk flooding the candle and damaging the piston group on your first run.
Calculation of power and load capacity of the boat
Determining the optimal power is a balance between the desired speed and the physical capabilities of the inflatable hull. maximum capacity Exceeding this limit is unacceptable, since inflatable tubes do not have the rigidity of metal and can deform under load when a sharp set of speed or hit a wave.
For boats up to 3 meters long, a motor with a capacity of 2-5 hp is usually enough. Such units allow you to reach a speed of about 10-15 km / h, which is quite comfortable for fishing or quiet walks. Boats with a length of 3-4 meters require 8-15 hp to plane effectively with one or two passengers. Larger vessels with a length of 4 meters need power from 18 hp and above to enter the planing mode with full load.
If you plan to take a lot of cargo with you, it makes sense to take a motor with a power reserve, but strictly within the limits of what is permissible for a transom.
| Boat length (m) | Optimum power (hp) | Maximum speed (km/h) | Type of operation |
|---|---|---|---|
| 2.0 – 2.9 | 2 – 5 | 10 – 18 | cruising, fishing in calm |
| 3.0 – 3.6 | 8 – 15 | 25 – 35 | Gleaning, river |
| 3.7 – 4.2 | 15 – 25 | 35 – 45 | Long-distance crossings, wave |
| 4.3. and more | 30 – 50+ | 45 – 60 | Expeditions, heavy load |
When choosing, you should also consider traction Sometimes a lower powered engine, but with a properly matched propeller, will perform better on a heavy boat than a more powerful unit with an inappropriate propeller geometry.
To go to the plane with a full load PVC boat length of 3.2 meters is often lacking standard 9.9 hp, and experienced water engines recommend looking in the direction of 15 hp or do "smothering" (removing restrictions) at 9.9, if the design allows.
Transcension design and motor fastening
The reliability of the engine attachment to the inflatable boat directly depends on the condition and design of the transom. Tranza It's a rigid insert in the stern of the boat that takes over all the thrust and vibration of the motor, it can be glued or removable, the glued transom provides more rigidity of the structure, but increases the weight of the boat when assembled, the removable transom is lighter, but requires careful check of the puff before each trip.
The height of the engine is controlled by a rod. The right position is when the anti-cavitation stove is 10 to 20 mm below the bottom of the boat. If the engine is set too high, the propeller will trap air, which will cause loss of speed and overheating. A landing too low will increase water resistance and reduce handling.
For inflatable boats, it is critical to use tetherIt's a strong cord that is attached to the ring on the boat at one end and the engine's dreadwid at the other end, and if the rod breaks or the screws are weakened, insurance will keep the engine from sinking.
- ⚓ Always check the tightening of the bolts of the rods before launching and after the first minutes of work.
- ⚓ Use rubber pads between the slug and the transucine to reduce vibration.
- ⚓ Make sure that the trans-board has no cracks and plywood layers.
⚠️ Attention: Never leave the motor suspended on the transom of an inflatable boat while parked on shore or when stored. Constant load from the weight of the engine can deform the transom and lead to depressurization of the seams.
☑️ Checking engine anchorages
Fuel system and flow rate
The efficiency of your swimming depends largely on the quality of the fuel mixture and the state of the fuel system. For two-stroke engines, you need to prepare a mixture of gasoline and a special oil for the use of the engine. boating In the proportion specified in the instructions (usually 1:25 or 1:50), the use of automotive oils or incorrect dosage leads to the formation of soak and engine failure.
Four-stroke engines run on pure gasoline, which makes it easier to refuel, but requires control of the oil level in the crankcase. Modern engines are equipped with efficient carburetors or electronic injection systems that minimize fuel consumption. On average, a two-stroke consumes about 300-400 grams per horsepower per hour, while a four-stroke engine uses 200-250 grams.
It's important to use gasoline with the octane number recommended by the manufacturer. AI-92The use of fuel with a lower octane number can cause detonation, and with a higher one - lead to overheating and burnout of valves (in four-stroke engines).
Special plastic tanks with a fuel filter-settler are used to store fuel on board, it is recommended to always have a spare tank or canister, as the flow can increase unpredictably when moving against the current or strong wind.
Fuel economy secrets
The most economical mode of operation of the engine is 70-80% of the maximum power. Full gas increases the flow rate by 30-40%, and the movement of the tension (at low speeds) can lead to coking candles. Keep the boat in planing mode for maximum efficiency.
Rolling screws: material and step
The propeller is the only element that converts engine power into motion, and it's the driving dynamics, the top speed, the boat's ability to plane, and the propellers are aluminum and steel. Aluminum screws They're cheaper and when they hit an underwater obstacle, they bend or break, saving the engine's dashwall, and steel screws are stronger, thinner and more efficient, but they can transfer power to the gearbox when they hit.
The key is the pitch of the screw, which is indicated by the second digit in the marking (for example, 9.8x10 step is 10 inches). Small pitch provides better traction at low rpm and fast access to the plane, but limits the maximum speed. Big step allows high speed, but the engine may not have enough rpm to accelerate the heavy boat.
The selection of the screw is an empirical process. The ideal is a screw in which the engine at full gas with normal load develops speeds close to the maximum specified in the instructions (usually 5000-6000 rpm).
- ⚓ For heavy boats and full load, choose a smaller pitch propeller.
- ⚓ For light boats and high-speed walks, increase the pitch of the propeller.
- ⚓ Always keep a shovel (a screw with a small step) in case of failure of the main one.
⚠️ Attention: If after replacing the screw you notice that the engine does not gain maximum speed (underload) or, conversely, "roars" and goes into cut-off (overload), it is urgent to replace the screw with a model with another step in order to avoid overheating and breakage by the piston.
A properly selected propeller can increase the speed of the boat by 5-7 km / h without increasing engine power and fuel consumption.
Off-season maintenance and storage
The durability of an outboard motor depends not only on the quality of the workmanship, but also on the proper maintenance. Regular maintenance includes changing candles, checking fuel filters and lubricating knots. Particular attention should be paid to the cooling system: after each trip through salt water, the motor must be washed with fresh water to prevent corrosion.
In preparation for winter storage, the two-stroke engine must be fully developed or preserved by pouring a mixture with an increased proportion of oil. A four-stroke engine requires changing the oil in the crankcase before winter, since the used oil contains acids that destroy parts during prolonged downtime.
Keep the engine is best in an upright position, covered from dust and moisture. Periodically, once a month, it is recommended to scroll the starter (on electric starters) or pull the starter cord so that the lubricant is distributed to the nodes.
Compliance with simple rules of operation will allow your engine to last for decades, delighting with stable traction and no problems at the most inopportune time.
Which motor is better to choose for fishing from the shore?
For fishing with frequent movements and pulling the boat ashore, a light two-stroke engine with a capacity of 2-5 hp is ideal. It can be easily removed and transferred in your hands. If fishing takes place on a large body of water with distillations, it is better to choose a four-stroke 9.9 hp for fuel economy and silence.
Can a outboard motor be used in salt water?
Yes, you can, but only if the motor has corrosion protection (usually labeled as "Salt Water Series" or similar) after each outing, be sure to flush the cooling system with fresh water and lubricate metal surfaces.
Why does the engine stop at high speeds?
This is most often a sign of fuel jelly, water in the tank, or a misfired spark plug, and it can also be a clogging of the fuel tank vent plug, creating a vacuum.
Do I need to run a new engine?
Yes, breaking in is mandatory for all types of engines, usually 10 hours of operation on the mixture with an increased proportion of oil (for 2T) and at variable speeds, avoiding full gas, which allows the parts to get lost in each other.