Choosing a power plant for an inflatable vessel is always a compromise between the speed, budget and technical limitations of the boat itself. Many beginners make the mistake of buying the most powerful unit available without thinking that the transom may not be able to withstand the load, and the control will become dangerous. engine-setting It requires an analysis of many factors, ranging from the length of the hull to the type of fishing or cruising planned.
The water industry offers a huge range of solutions, and it can be difficult to figure them out immediately. You have to decide which is more important: ease of carrying or fuel economy, maximum speed or long-distance travel. In this article, we will discuss all the aspects that will help you not waste money and get the boat you want.
Analysis of technical specifications of the boat
The first step is always to look at your boat's passport, because that's where the power limit is. PVC boats It tests and specifies the maximum allowable horsepower, which is strictly forbidden because of the risk of transom failure. If you install a too powerful engine, you risk not only damage the structure, but also to be denied registration of the vessel in GIMS, as this violates the certification conditions.
There is a concept of optimal power, at which the boat goes to planing with full load, but remains manageable. For most inflatable models with a length of 320-360 cm, the “golden mean” is the range from 9.9 to 15 hp, which allows you to comfortably move together with the load. Less power will lead to the fact that the boat will be constantly in displacing mode, consuming fuel and creating a high wave, but not developing speed.
⚠️ Warning: Never ignore the engine weight limit specified in the boat instructions. Excess weight on the transom changes the different, lifting the nose too high, which can lead to a wave and tipping.
It is also important to consider the design of the transom: a rigid glued transom can withstand more loads than a hinged one. If you own a low-pressure inflatable floor boat (LBBB), then the power requirements may even be stricter due to the geometry of the hull. Motor traction It must correspond to the area of the bottom to effectively lead the boat to the plane.
Two-stroke or four-stroke: the eternal dilemma
The choice between a two-stroke (2T) and a four-stroke (4T) engine determines the nature of your boat's operation. Two-stroke engines are traditionally lighter, cheaper to buy and easier to maintain, making them ideal for small inflatable boats that often have to be carried by hand. They run on a mixture of gasoline and oil, which adds to the hassle in preparing for the season, but provides excellent traction at low revs.
Four-stroke counterparts, by contrast, are quieter, fuel efficient, and don't require a gasoline blend. However, they can weigh 30-50% higher than two-stroke counterparts of the same power. For boats less than 3 meters long, this weight becomes critical, making descent and loading into a car a real test for the back.
On the other hand, for boats longer than 3.6 meters, which are often used for long-distance crossings or trolling, the four-stroke becomes the choice without alternative: its resource is usually higher and vibrations are minimal, which is especially important when working long on small strokes. Engine resource The 4T often reaches 3,000-4000 motor hours versus 1,500-2000 for the 2T with proper care.
⚠️ Warning: When buying a used four-stroke engine, be sure to check the state of the oil. The presence of an emulsion (light brown "porridge" on the probe) indicates that water enters the crankcase, which indicates a serious malfunction.
The myth of fuel consumption
There's a common belief that two-strokes always eat more. It's not quite true. Modern two-stroke engines with E-TEC or OptiMax systems can be more economical than older four-strokes. However, on average, the 4T saves about 20-30% of fuel over long distances.
Calculation of the required power and thrust
To be sure, a simplified formula is used to determine whether a motor will work, it is estimated that a single person with minimal gear needs about 1 hp for every 25-30 kg of total weight to get on board, and if you plan to carry two adults, equipment, anchor and fuel, the total weight can easily reach 250-300 kg.
For this weight, the minimum power for confident planing will be about 10-12 hp If power is not enough, the boat will "dig" the wave with its nose, creating a dangerous situation. Below is a table of approximate correspondence of the length of the boat, the number of people and the recommended power of the engine.
| Boat length (cm) | Number of people | Recommended power (hp) | Typical speed (km/h) |
|---|---|---|---|
| 280 - 300 | 1-2 | 2 - 5 | 15 - 25 |
| 320 - 340 | 2 | 9.9 - 10 | 30 - 35 |
| 360 - 380 | 2-3 | 15 - 18 | 35 - 45 |
| 400+ | 3-4 | 20 - 30 | 45 - 55 |
It's important to understand that these numbers are relevant for standard conditions and still water, and when there's a strong wind or against the current, power supply becomes critical. Engine power Not only is it speed, but it is also your safety in difficult weather conditions.
Always buy a motor with a power reserve of 10-15% of the minimum required to enter the plane. This will prolong the life of the engine, as it will not run to the limit.
Selection criteria: weight, management and reliability
The weight of an outboard motor is one of the main parameters for PVC boat owners. If you plan to change water bodies often, dragging the boat with a drag or lifting it to a high shore, every extra kilogram will be felt. Light models up to 20 kg (usually 2-5 hp) can be installed and removed independently, whereas engines over 30 kg require an assistant or a special cart.
Control also plays a role. Low-power motors are usually rumpled, which is convenient and cheap. Higher-power models, especially if you want to install a sonar and a navigator, may require remote control, which involves laying cables and installing a steering mechanism, which complicates the design but increases comfort.
Brand reliability Popular brands like Yamaha, Tohatsu, Mercury, Suzuki have a well-developed service network, and buying an exotic Chinese brand can be a problem if you need a specific pad or sensor that no one carries around in the season.☑️ Checklist before buying an engine
Overview of popular brands and models
The outboard motor market is saturated with offers, but time-tested manufacturers remain the leaders. Tohatsu and Yamaha For example, the Tohatsu M9.9B is a legend among fishermen, known for its indestructibility and maintainability. Yamaha 9.9 FMHS is famous for excellent traction and high-quality assembly, although it is more expensive than competitors.
Chinese manufacturers such as Hidea, Sea-Pro or Mikatsu offer attractive prices and often copy proven Japanese designs. Over the past 5 years, the quality of their products has increased, and many models are exact copies of Tohatsu engines. For the budget segment, this is a great option, allowing you to save up to 30-40% of the cost without critical loss of reliability.
Failure statistics show that 80% of problems with engines of any brand are associated with violation of the rules of running and the use of low-quality fuel, not with factory defects.European brands, represented mainly by the Mercury (US/Europe) or Selva range, often offer unique solutions in the field of management and environmental friendliness. The choice of a particular model should be based not only on marketing slogans, but also on real feedback from owners in your region.
Service and seasonal storage
The proper operation starts with running in. A new engine, whether it's a 2T or a 4T, requires a gentle operation for the first 10 hours. You can't just give full gas; you have to alternate rotations, let the parts get lost. Ignoring this stage is a sure way to cut back. engine twice.
At the end of the season, you have to conserve the engine. For two-strokes, that means making a carburettor mixture to avoid coking, and for four-strokes, you have to change the oil, because the used oil contains acids that destroy parts when you park, and it's better to store the unit upright in a dry room.
Regular replacement of fuel filters and use of a fuel stabilizer during long-term storage prevents 90% of launch problems in the next season.
How to properly preserve the engine for the winter?
To preserve, you need to drain old oil (for 4T), treat the cylinders with a preservative, pour fresh oil, produce fuel from the carburetor and lubricate all moving parts with a special lubricant. It is also recommended to remove the candle and drop some oil into the cylinder, turning the crankshaft.
Why does the engine stop at high speeds?
Most often, the cause is clogging of the fuel filter or jelly carburetor, and it is possible to suck air through the gasket or leaky fuel hose. In two-stroke engines, the cause can be the wrong proportion of oil and gasoline.
Can I use AI-95 gasoline?
Yes, modern outboard motors are designed for gasoline with an octane number of 92-95. However, it is important to monitor the freshness of the fuel. Gasoline that has been in the can for more than 3-6 months loses its properties and can lead to unstable engine operation.
What to do if the motor falls into the water?
Don't try to start the engine right away! You need to thoroughly wash it with fresh water (if the fall was in salt water), remove the candles, blow out the cylinders, change the oil and only after completely drying and diagnosing try to start.
How often should you change the oil in the gearbox?
The oil in the gearbox (lower gear) is recommended to change once a season or every 100 motor hours. When replacing, pay attention to the color of the oil: if it has become milky, then the sealing of the omentums is broken and water enters the gearbox.