Choosing an engine for a small inflatable or light metal boat is always a search for a balance between power, weight and comfort of operation. Four-stroke outboard motor up to 5 hp Today, it is the gold standard for such tasks, offering efficiency and low noise levels. Unlike its two-stroke counterparts, these units work quieter and cleaner, which is especially important for anglers and those who like to relax on the water.
However, despite the popularity of the class, beginners often face many questions: Which model to choose? Why are they heavier than two-strokes and is it worth the overpayment? In this article, we will discuss in detail the technical nuances, the advantages of design and give practical recommendations that will help you make an informed decision when buying.
Understanding the principles of work combustion engine And four-bar is the key to a long, seamless operation, and there's no need to mix gasoline with oil, which makes it much easier to refuel, but it requires a lot more attention to the oil level in the crankcase, so let's dive into the details so that your day on the water doesn't turn into a fight against the machinery.
Advantages of four-stroke construction
The main advantage of this technology is the separation of intake, compression, combustion and exhaust processes, which allows for a more complete combustion of the fuel mixture, which directly affects the combustion of the fuel mixture. fuelOwners often note that a 1.2-liter tank is enough for a full day of fishing in economical mode, whereas a two-stroke analog would require refueling.
The second, equally important, aspect is acoustic comfort, and the engine that's running makes a smooth, low-frequency hum that doesn't irritate the ears or scare the fish. Yamaha, Mercury and Hidea pay special attention to soundproofing of the casings, turning the engine into background noise, barely distinguishable against the background of water splashing.
And the four-stroke circuit also means that you don't release any unburned oil into the water, and that makes the engine environmentally friendly, which is critical for water bodies with strict environmental regulations or when used in protected areas, and you don't leave behind rainbow film that spoils the view and the environment.
⚠️ Attention: Despite the presence of a lubrication system, the first start of the new engine should be in a gentle mode.
Weight and dimensions: design compromises
The most obvious drawback that users face when switching to a four-stroke is weight, which includes a full-fledged lubrication system with a crankcase, an oil pump and a valve mechanism, all of which add mass, making the motor 30-40% heavier than a two-stroke analog of the same power.
For models with a 5 hp weight ranges from 24 to 27 kilograms. For one person, especially if you need to drag the boat around often or lift the engine to a high side, this can be a serious challenge. However, manufacturers try to minimize this disadvantage by using modern aluminum alloys and composite materials for lower units.
It is important to take into account not only the mass of the engine itself, but also its dimensions. Overall dimensions Four-strokes are often larger due to the larger bottom and cooling system. When transported in the trunk of a car, this can play a crucial role, especially if you have a compact hatchback or sedan.
How to reduce the impact of weight on management?
There are special transom wheels that are attached to the engine's lower unit, which allow you to roll the motor on a solid surface without lifting it on weight, and there are also models with a remote tank, but in a class under 5 hp, they are rare, because the built-in tank is usually enough.
If weight is a critical factor, you should pay attention to the models with day-wound (L), which may have a slightly different weighting, or consider an aluminum screw that is lighter than steel, but the only way to make a difference is by choosing a different power or engine type.
Technical specifications of popular models
The market offers a variety of options from big brands and their Chinese counterparts, and to avoid getting confused by the numbers, we have compiled a comparative table that shows the averages for this power class, and the data may vary slightly depending on the specific modification and year of production.
| Brand/Model/Model/ | Power (hp) | Weight (kg) | Workload (cm3) | Launching system |
|---|---|---|---|---|
| Yamaha F5CMHS | 5.0 | 27.0 | 112 | Manual |
| Mercury F5M | 5.0 | 26.5 | 112 | Manual |
| Hidea HD-F5.0BMS | 5.0 | 24.5 | 98 | Manual |
| Tohatsu MFS5C | 5.0 | 27.0 | 112 | Manual |
As you can see from the table, working-room Most market leaders are similar, about 100 cubic centimeters, the best measure to achieve declared power while maintaining reliability, and the difference in weight is often due to the thickness of the lower unit metal and the design of the active part.
It is worth noting that many modern models have an electronic ignition system (CDI), which provides a stable spark at any temperature and humidity, which eliminates the need to check the gap of candles before each exit, although state control is not necessary. spark plug It is recommended to be held regularly.
When buying, pay attention to the presence of a built-in fuel filter-sludge. In the class up to 5 hp, it is often combined with a fuel crane and allows you to visually assess the purity of gasoline.
Service and preparation for the season
A four-stroke engine requires a disciplined approach to maintenance, a focus on the level and quality of the engine oil, and oil replacement is the first and most important procedure that the owner must master, usually after the first 5-10 hours of running, and then every 50-100 hours or once a season.
The replacement process is simple, but it requires some tools, you'll need a pumping syringe or a pump, and you'll need a funnel to fill the new oil. It's important to use oils with the viscosity recommended by the manufacturer, most often it's the same. SAE 10W-30 or SAE 10W-40 admittance FC-W.
- 🛠️ Check the state of the spark plug: the coar should be brick in color, the electrode is intact.
- 💧 Inspect the water pump: make sure that a stream of water comes from the control hole when working.
- 🔩 Check the tightening of the screws of the lower unit and the casing, as vibration can weaken them.
- ⛽ Clean the fuel filter and blow the carburera jellyfish with compressed air.
Special attention should be paid to the cooling system: water withdrawal occurs through holes in the lower unit, where sand, algae or small pebbles can be stuffed, and regular washing with fresh water after operation in salty or polluted water will prolong the life of the pump impeller and cooling shirt.
☑️ Preparation of the engine for winter storage
Operational and safety nuances
The low-power four-stroke has its own specifications: because you don't have to mix fuel, you get a lower risk of fueling errors, but you get a dry run. If you drop below critical, you can jam in seconds. Some advanced models have emergency stop sensors, but you don't have to rely on them.
Transporting the engine also requires compliance. Four-stroke engines can be transported in any position, unlike two-stroke engines, which require a strictly vertical position. However, to avoid leaking oil through the sapoon or getting it into the combustion chamber, it is recommended to keep the engine vertically or on a special transport wheel.
⚠️ Attention: Never start the engine without immersion in water or without connecting to an artificial cooling system. Dry operation will instantly disable the impeller of the water pump and can damage the osteoils.
When driving a boat, it's important to remember the inertia of a four-stroke engine, which is slower to gain momentum and has a more pronounced thrust at low speeds. This requires getting used to maneuvering in narrowness. A sharp gas discharge can cause the engine to stop if the idling system is not set up correctly.
Repairability and resource
The resource of a four-stroke engine, when properly maintained, is significantly higher than that of a two-stroke engine, and the absence of an aggressive fuel mix and the presence of a full-fledged rubbing vapor lubrication system allows such engines to run 1,500 to 2,000 hours before major repairs. For amateur use, which is 20-30 hours a year, this means decades of service.
But the design is more complicated. The cylinder head contains valves, pushers and skewers that require periodic adjustment of the thermal gaps. If you hear a ringing thud that is increasing with rev, it's probably time to adjust the heat gaps. valve-gapThis operation requires a set of probes and basic mechanical skills.
In the event of serious breakdowns, such as valve burn or crankshaft wear, repairs can be expensive, so it is important to monitor fuel quality and avoid overheating. Using gasoline with an octane number below the recommended (usually an AI-92 or an AI-95) can lead to detonation and destruction of the piston group.
Timely oil change and the use of quality fuel are two of the main factors that determine the durability of your four-stroke engine.
Can a four-stroke motor be used in shallow water?
You can use it, but with caution. Four-stroke engines often have longer lower units. When lifting the engine to pass through shallow water, make sure that the water intake hole remains underwater, otherwise the pump will remain without lubrication and cooling. For very shallow water, there are special "small-water" screws or lower unit nozzles.
Which petrol is better to fill: 92nd or 95th?
Most modern engines up to 5 hp are designed for AI-92 gasoline. Using AI-95 will not give a gain in power, but can lead to more severe combustion and overheating if the engine is not adapted to a high octane number.
Why does the engine smoke on the first run after winter?
A small short-term smoke can be caused by burning out of the preservation oil that entered the cylinder during storage, or by the residue of oil in the silencer. If the smoke is white and thick all the time, it is a sign of oil entering the combustion chamber (wear of the rings or oil caps).