Choosing an outboard motor for a boat is always about balancing power, reliability and efficiency. In the 50 hp segment, one of the most popular and time-tested solutions is a model from Japanese giant Honda. BF50DK4 LRTU It deserves special attention, as it combines the classic reliability of the brand and modern environmental standards.
This model is a four-stroke unit, which has long established itself as a "workhorse" for owners of boats with a length of 4 to 6 meters. Indexation in the model name carries important information about the technical features of the device, which we will talk more about below.
Owners often look for information about the long leg and electric start version, as it is the most comfortable option for long walks on the water. Let's understand what lies behind the complex alphanumeric code and why this motor is still relevant in the market.
Decoding of model marking
Understanding the letter marks helps not to get confused in catalogs and choose the equipment that will fit your boat. Honda BF50DK4 LRTU It is not just a set of symbols, but a precise specification.
The number 50 indicates a maximum power of 50 horsepower. D It means that you have an electric starter, which eliminates the need to pull the rope with your hands, especially in cold weather, and the number 4 at the end of the model name confirms that we have a four-stroke engine.
The most important part for installation is the abbreviation LRTUHere. L Long stands for 508 mm, which is ideal for high-transe boats. R Remote indicates a remote tubel gas, T (Tilt) - to the tilt system, and U These parameters are critical for compatibility with the hull of the vessel.
Why is exhaust through screw or lower unit important?
The top exhaust (U) in this model means that the exhaust gases are coming out above the waterline, which reduces noise in the cabin of the boat, but may be less effective for thrust at low revs compared to exhaust through the screw (P).
Knowing these nuances will allow you to avoid buying a motor that will not physically stand on a transom or require expensive revision of the control system.
Technical specifications and capabilities
The engine is based on a time-tested 822 cubic centimeter cylinder block, a two-cylinder unit with an upper camshaft (Chamshaft).SOHC), which provides excellent traction at low and medium speeds.
The ignition system here is electronic, with transistor control (TCIIt does not require adjustment of gaps and is highly reliable even in high humidity and salty environments.
- 🚀 Power: 50 hp at 5500 rpm
- ⚖️ Weight: 108 kg (including screw and oil)
- ⛽ Tanks: external 25 liters (standard equipment)
- 🔄 Transmission ratio: 2.08:1
It's important to note that the cooling system is a forced water system with a thermostat, which allows the engine to get to the operating temperature faster and keep it stable, which reduces the wear of rubbing parts.
The TCI system provides stable spark formation even when candles are wet, which is critical for water safety.
Advantages of four-stroke construction
The transition to four-stroke engines has become the standard for many water-engines, and the model is not. BF50DK4 And it's a very clear demonstration of why this happened, and the main difference from two-stroke analogs is that there's a separate lubrication system.
You don’t have to cook a fuel mixture by mixing gasoline with oil. Carter oil It's poured separately and it changes the rules, like in a car, which makes it much easier to get ready to go out.
In addition, the four-stroke cycle provides a quieter run, vibrations are minimized thanks to balancing shafts, which makes fishing or cruising more comfortable, and idling noise levels do not interfere with conversation.
The environmental aspect is also not to be ignored: the combustion of fuel is more complete, and the release of harmful substances into the water is minimal, which allows the use of this motor in water bodies with special conservation status.
Fuel consumption and economy
The question of engine appetite is always acute, especially given the current prices for fuel. the four-stroke scheme Honda BF50DK4 LRTU is characterized by high fuel efficiency.
At cruising speeds, which are usually around 4,000-4,500 rpm, the flow rate is about 12-14 liters per hour, and on economical trolling, this figure can fall to 2-3 liters.
In comparison, two-stroke engines of similar power in similar modes can consume 30-40% more fuel, savings are achieved by not losing the working mixture through the exhaust windows.
| Mode of work | Turnover (rpm) | Speed (km/h)* | Expenditure (L/h) |
|---|---|---|---|
| Idle move | 900 | 5 | 0.6 |
| trolling | 2500 | 8-10 | 2.5 |
| Cruiser | 4500 | 35-40 | 13.5 |
| Full gas. | 5500 | 48-50 | 18.0 |
* Speed is indicated for approximately 4.5-meter long PVC boats with full load.
Security and protection system
Japanese engineers have put a lot of emphasis on protecting the engine from accidents. Oil AlertIt monitors the pressure level of the oil.
If the pressure drops below the critical point, the system automatically reduces engine speed, preventing the piston group from jamming, giving the owner time to react and shut down the engine before fatal damage occurs.
⚠️ Warning: Never ignore the sound of the Oil Alert system. Continued driving with the alarm on can lead to a complete failure of the engine without the possibility of recovery.
It also has overheating protection, a temperature sensor that monitors the condition of the water jacket, and when the temperature rises critically, the motor will also reset to avoid deformation of the cylinder heads.
Check the water urinal regularly when starting, and the lack of a jet is the first sign of pump problems, even if the alarm has not yet gone off.
Maintenance and maintenance
The engine life depends on the quality and timeliness of service. Honda BF50DK4 LRTU does not require complex special equipment for basic procedures.
The first maintenance is usually done after 20 hours or one month of operation, during which time the engine oil is replaced and all connections are checked, then the intervals are increased to 100 hours or one season.
☑️ Seasonal engine maintenance
It is important to use only the manufacturer's recommended liquids. This engine is suitable for API oil classification SG, SH, SJ or SL with a viscosity of 10W-30.
Candle gaps also require periodic checks: the optimal distance between the electrodes is 0.7-0.8 mm. Using candles with the wrong potassium number can lead to detonation or fouling with soot.
Typical malfunctions and their elimination
Despite the high reliability, the equipment can break down, and most often owners face problems with the cooling system or fuel system.
Clogging of carburetor fuel jellyers is a common problem when using poor-quality gasoline or storing a full-tank engine in the off-season. The old fuel is oxidized and converted into resins that clog thin channels.
⚠️ Warning: For long-term storage (more than 1 month), be sure to generate fuel from the carburetor before the engine stops or use a fuel stabilizer. The remaining gasoline in the float chamber will evaporate, leaving a sediment.
Start-up problems may also be related to battery discharge. LRTU It's powered by an electric starter, and the battery is critical, and a weak charge can turn the motor, but it doesn't spark enough power.
Conclusion and summary assessment
The Honda BF50DK4 LRTU is a classic example of an engineering approach that prioritizes durability and predictability, not a racing car, but a reliable tool for work and recreation.
It is chosen by those who value silence on water and do not want to waste time mixing oil, and the high residual value in the secondary market confirms the model's status as a liquid asset.
If you’re looking for a mid-sized outboard motor that will last decades with proper care, this model remains one of the best candidates in its class.
Proper preservation for the winter prolongs the life of the carburetor engine by 30-40% compared to storage "as is".
Which octane is best used for the Honda BF50?
The manufacturer recommends the use of unleaded gasoline with an octane number of at least 92 (research method) or 87 (motor) fuel with a higher octane number (AI-95, AI-98) is allowed, but does not provide significant advantages for an atmospheric engine of this degree of compression.
How often should you change the oil in the gearbox?
The oil in the gearbox (low gear) is recommended to be changed once a season or every 100 motor hours. At the first maintenance (20 hours), replacement is required to remove the metal shavings after running. Control the color of the oil: if it has become milky, then the leakage of the oils is broken and water is injected.
Can this motor be used in salt water?
Yes, the motor is adapted for use in salt water, corrosion resistance is enhanced by special coatings and the use of stainless steels in key nodes, but after each outing, be sure to wash the cooling system with fresh water, connecting the motor to a barrel or water supply.