Finding the optimal boat-engine 340 A 3.4-meter inflatable boat is the middle ground for most anglers and water lovers, but that size requires careful consideration of the power plant choice. A too weak unit will not allow full-load plane, and excess power can lead to transomper destruction or even tipping over the vessel on the wave.
Unlike larger models, where power reserve is easy to calculate, for the 340th boat, every horsepower counts. It is important to consider not only the passport power of the engine, but also its weight, the type of lower unit leg and the specifications of the propeller. In this article, we will discuss in detail the technical details of the selection of the engine, so that your stay on the water was safe and comfortable.
There is a common misconception that any low-power electric motor or petrol “two-stroke” is enough for a PVC boat of this size, but the realities of operating on rivers with currents or large reservoirs dictate their conditions. Critically important correctly calculate the displacement and resistance of the body, so as not to remain a few kilometers from the shore with the engine operating at the limit.
Technical specifications of boats with a length of 340 cm
Before I go to the store for boat-engineThe 340 cm boats come in two main designs: PVC inflatable and all-metal (aluminum) boats, although they are the same length, their physics and thrust requirements are radically different. PVC boats have a high sailability and flexible bottom, which creates additional resistance to water.
Aluminum "Kazanki" or "creams" of this length, on the contrary, have a rigid body and often keeled contours, allowing better cutting of the wave, but requiring greater traction for planing due to greater own weight. The maximum power for PVC boats of 340 cm rarely exceeds 15 hp, whereas the metal can carry up to 20-25 hp. Exceeding these limits is fraught with deformation of the transom board in soft sides or a dangerous defferent on rigid housings.
Also consider the type of bottom: Inflatable floor (BND) or plywood/aluminum paioles have different effects on hydrodynamics. engineIf you plan to use a boat together with full gear, weight load will be the decisive factor in choosing thrust.
Remember that the manufacturer always gives the maximum power allowed on a tag sewn to the cylinder or on the transom. Ignoring this data can lead to a loss of warranty and, more importantly, to an emergency situation. The table below compares the requirements for different types of enclosures.
| Type of boat 340 cm | Max power (hp) | Recommended engine weight | Features of operation |
|---|---|---|---|
| PVC (NDD) | 9.9 - 15 | 35 kg | High sail, soft move |
| PVC (Pyolas) | 15 - 18 | 40 kg | Hard bottom, better glossing |
| aluminum | 18 - 25 | 50 kg | High inertia, resistance to wave |
Power calculation: two-stroke or four-stroke?
The eternal dispute between the adherents two-stroke and four-stroke engines are especially relevant for boats 3.4 meters long. Here the key factor is weight. Two-stroke engine with a capacity of 9.9 hp weighs an average of 25-28 kg, which makes it easy to install and remove one person. Four-stroke analogue of the same power will be heavier by 10-15 kg, which significantly changes the weight on a small boat.
But when you look at 15 hp motors, the weight difference is flattened out, and the benefits of four-stroke design are clear: they're quieter, more fuel efficient, and don't require a fuel mix. four-stroke It will be a choice, despite the higher price and complexity of the service.
If your goal is to get the boat to the fishing site quickly and then to fish on electric or drift, the two-stroke will be more practical. It is easier to transport (you can put on your side) and cheaper to repair. with., but a comfortable speed will have a unit from 10-12 hp.
For a boat of 340 cm, the priority is often the weight of the engine, so two-stroke models up to 10 hp remain the leaders of sales due to mobility.
When choosing, you should also pay attention to the presence of a forced oil lubrication system (for 2T) or a separate tank (for 4T), which eliminates the need to constantly mix gasoline with oil in the right proportion, which is especially important in the field.
Criteria for the selection of transom and suspension device
Installing the motor on a boat 340 cm requires careful attention to the condition of the transom. the height of the transom board is standard 381 mm (15 in) or 508 mm (20 in). For boats of this size, the short lower unit (S) is most often used, since the long leg (L) will create excessive drag and sailing, and also increase the weight of the entire structure.
The motor is fastened either by means of rods or through a transition plate. Strubsins are convenient for quick removal, but on powerful engines (15+ hp) they may not provide sufficient rigidity, especially on aluminum boats. graffitiIt distributes the load over a larger area and allows you to install additional accessories such as a sonar or GPS sensor.
⚠️ Attention! When installing the engine, make sure that the anticavitacines plate is 1-2 cm below the bottom of the boat when driving. Too deep landing of the screw will lead to loss of speed, and too high will lead to air sucking and engine overheating.
Also critical is the diving angle of the lower unit (differentiation); the right trim allows the boat to go out faster and keep the plane smooth; on many modern engines, the angle adjustment is done by rearranging the pin in the holes in the lower unit or using a hydraulic lift on more powerful models.
Effect of the screw type on speed and traction
A regular propeller, complete with the motor, is often a compromise solution. For a 340 cm boat that can be used for both fishing (where low-speed traction is important) and cruising (where speed is needed), it makes sense to experiment with the propeller's pitch. Reducing the propeller's pitch will increase traction and allow for faster plane at full load, but reduce maximum speed.
- 🌀 Aluminum screws: Cheaper, lighter, when hitting an obstacle bend, protecting the gearbox, but they are difficult to accurately restore.
- 🌀 Stainless steel: More expensive, heavier, provide better acceleration dynamics and maximum speed, but with a strong impact can transfer the load to the shaft.
- 🌀 Composite screws: A modern solution combining flexibility and strength often comes in the runoff with new engines.
The selection of the screw is an empirical process. The ideal option is when the full-gas motor (WOT) develops the speed specified in the data sheet (usually 5000-6000 rpm). If the revolutions are lower, the screw is "heavy" (big step), if higher - "light". Operating the engine in unheated mode or at too high speeds without load reduces the resource. piston group.
What is cavitation and how is it dangerous?
Cavitation is the formation of vapor bubbles in local pressure-reducing areas around the propeller blades. When these bubbles collapse, a microhydro shock occurs, which destroys the propeller material (cavitation erosion) and creates characteristic noise. For a boat, 340 cm cavitation often occurs when the engine is not installed correctly in height or when sharp turns at high speed.
Electric motors: alternative to gasoline for the 340th boat
In recent years electric motors They are a serious alternative to gasoline, especially for PVC boats with a length of 340 cm They are silent, do not require fuel, do not emit exhaust gases and are much easier. For quiet fishing in small ponds electric motor thrust 30-50 lbs (pounds of force) will be enough.
The main limitation here is battery life and speed: the electric motor will not allow you to reach high speeds (usually up to 5-7 km / h), and to recharge the batteries will require access to the power grid. However, if you fish on pressed water bodies or at night, where the noise of the gasoline engine is unacceptable, the train will be the best choice.
It's important to pick up the battery right. traction-carrying (GEL, AGM or LiFePO4), which can give off current in small portions for a long time. Starter car batteries for this purpose are not suitable and will quickly fail.
Use lithium (LiFePO4) batteries for electric motors – they weigh 2-3 times less than lead analogues of the same capacity, which is critical for a small boat 340 cm.
Service and preparation for the season
The durability of the engine is directly dependent on the quality of service. For outboard motors, especially two-stroke ones, it is critical to use quality oil labeled TC-W3. Cheap mineral oils lead to the formation of soak on candles and in the exhaust windows, which reduces power and resource.
Before each season, you need to carry out prevention: check the state of the spark plug, lubricate friction points, check the fuel hoses for cracks. For four-stroke engines, it is mandatory to monitor the level of oil in the crankcase and its timely replacement (usually every 50-100 motor hours).
- 🔧 Thermostat check: Make sure the motor reaches operating temperature but does not overheat.
- 🔧 lower unit lubricant: regularly syringe the lubricant into the gearbox through special holes (if provided by the design).
- 🔧 Preservation: When stored in winter, be sure to drain water from the cooling system or use antifreeze, and treat the outer surfaces with a preservative.
⚠️ Attention! Never keep a full-gasoline engine indoors. Fuel can oxidize during the season and coke the carburetor, use fuel stabilizers or fully produce gasoline before canning.
Regular visual inspection of lower unit for water entering the oil (emulsion on the probe) will help prevent expensive repairs of the gearbox. Water in the gearbox most often gets through the oment of the paddle shaft when hit by underwater obstacles.
☑️ Preparation of the engine for the first start
Security and legal aspects
Operating a boat with an engine requires safety. On a boat with a powerful engine, a 340 cm life jacket is mandatory for each passenger. Even if you are a great swimmer, cold water and heavy clothing can play a cruel joke. It is also recommended to have an anchor, an end (falin) and a means of drawing water.
In Russia and many CIS countries, boats with engines up to 10.88 hp (8 kW) and weighing less than 200 kg do not require registration with the GIMS and the availability of rights to drive. This makes the “boat 340 cm + engine 9.9 hp” extremely popular among law-abiding citizens.
Always carry your boat and motor documents, as well as a life jacket. The rules of the road on water bodies have not been canceled: observe the speed limit near the shore, give way to large boats and do not go out in stormy weather.
Can I put the 15 hp engine on a boat marked 9.9 hp?
Technically, it is often possible if the transom will withstand weight and power, but legally it is a violation. 15 hp engine is usually programmatically or physically (through the valve) limited version of 9.9 hp. Removing restrictions equates to tuning, which requires reworking documents or leads to a penalty during inspection.
What is the best gasoline to use for a motor?
Use only fresh AI-92 or AI-95 gasoline (depending on the manufacturer's recommendation) with an octane number not lower than required. Avoid fuel with an expired shelf life (more than 1-2 months), as it loses its properties and forms resins. For two-stroke engines, the quality of the oil mixed with gasoline is critical.
Why does the engine stop at high speeds?
There may be several reasons: clogging of the fuel filter, problems with the ignition system (candle, coil), air pumping into the fuel system or poor-quality fuel mixture, and it is also worth checking whether the exhaust hole does not block water when the engine lands too deep.
Do I need to register a 340 cm boat with an electric motor?
If the weight of the boat in running order does not exceed 200 kg and the power of the electric motor is less than 8 kW (which is true for 99% of electric motors), registration with the GIMS is not required.