Choosing an outboard motor for a small PVC boat or a light boat is often a difficult task, requiring a balanced decision. Komatsu outboard motor 9.9The turbocharged engine has proven to be a reliable model for water engines, combining a time-tested two-stroke design with modern engineering solutions aimed at reducing vibration and fuel consumption.
Many owners value this unit for its maintainability and availability of spare parts on the market. Komatsu 9.9 It is based on a proven cylinder block that is easily upgradeable, making it a popular choice for those who love technical creativity. In this article, we will discuss in detail the technical nuances, features of operation and hidden potential of this power plant.
It is worth noting that the popularity of the model is due not only to the price, but also to real endurance in harsh operating conditions. Two-stroke engine This class is ideal for fishing and cruising, where it's not about top speed, it's about confidence in starting and running at low speeds, and if you look at the details, you'll see why this engine has been on the market for many years.
Technical specifications and design features
The power plant is based on a two-cylinder two-stroke engine with a displacement of 171 cubic centimeters, which provides excellent low-speed traction, which is critical for planing with a full load of the boat. carburetor mixture It is configured to work with AI-92 gasoline mixed with oil in a standard ratio of 1:50, which simplifies maintenance in the field.
The cooling system is particularly noteworthy, and the motor is equipped with a forced water pump that effectively removes heat even when operating at high speeds for long periods of time. thermostatThe engine is designed to warm up faster and maintain optimal temperature, reducing the wear of rubbing parts, weighing about 34 kilograms, making it relatively easy to transport in the trunk of the car.
An important element is the Capacitor Discharge Ignition (CDI) system, which does not require an external battery to start, which makes the motor fully autonomous and ready to work at any time.
| Parameter | Meaning |
|---|---|
| Power | 9.9 hp (7.4 kW) |
| Workload | 171 cm |
| Maximum speeds | 4500-5500 rpm |
| Launching system | Manual (Candle) |
| Weight. | 34 kg |
The secret to high traction
Why are two-stroke engines so popular in this class? The fact is that the stroke occurs with each rotation of the crankshaft, not through one, as in four-stroke motors, which gives almost two times the gain in specific power with less weight of the structure.
Possibility of increasing power to 15 hp
One of the most discussed topics among owners is the possibility of increasing power. Komatsu 9.9 The engine is designed to be designed with a safety margin to remove more power without critically reducing its life. In fact, the 9.9 hp limit is often imposed programmatically or mechanically (e.g., a limiter in a carburetor or exhaust system) to fit into certain tax or registration categories.
The modernization process, often referred to as “dekulakization”, involves removing the physical constraints on the fuel mixture and exhaust gases. In some versions, it is enough to replace the petal valve or modify the exhaust system to start producing the 15 hp declared by the manufacturer. modernization It requires a precise understanding of the processes that take place inside cylinders.
⚠️ Attention: Self-increased power removes the engine from the warranty and can lead to accelerated wear of the piston group, if not enriched fuel mixture accordingly. Be prepared for the fact that the engine life will be reduced if you constantly operate at the limit.
After the refinement, the boat begins to go more confidently into planing, and the maximum speed increases by 3-5 km / h depending on the type of screw and loading the vessel.
Fuel consumption and efficiency of operation
Economy is one of the key factors when choosing an outboard motor. Komatsu 9.9 It shows the average fuel consumption of engines in this class: in trolling or low-speed mode (about 3000 rpm), the engine consumes about 2.5-3 liters of fuel mixture per hour, which allows you to comfortably fish all day on one tank of 12 liters.
When going to full gas and moving on the plane, the flow rate increases to 4-5 liters per hour. If the mixture is too poor, the engine can run unstable and warm up, if rich, the sun will grow on candles and gasoline consumption.
To reduce costs, many experienced water engines recommend using quality synthetic oils for two-stroke engines, which provide better lubrication and burn with less sodium, which has a positive effect on work. exhaust and spark plugs.
Use gasoline with an octane rating of at least 92 and be sure to add oil to within a milliliter. A ratio of 1:50 means 20 ml of oil per 1 liter of gasoline. The accuracy of mixing prolongs the life of the engine.
breaking in: rules and stages
Proper running is the key to a long life of any engine, and Komatsu is no exception. The process of working out rubbing parts requires strict adherence to time intervals and load regimes. The first 10 hours of operation are critical, and during this period, the process of working is critical. The piston group forms its final conjugation.
During the first two tanks (about 10 liters of the mixture), it is recommended to operate the engine at a speed of not more than 50% of the maximum power, which means that you can not open the throttle more than half, then, in the next 8 hours, you can briefly increase the speed, but avoid long-term operation at full gas.
☑️ Checklist of successful break-in
After the break-in stage is completed, it is strongly recommended to replace the spark plugs and check the tightening of all bolt joints, especially on the lower unit and carburetor mounts. Vibrations in the first hours of operation can weaken the threaded joints, so hood It is a mandatory procedure.
⚠️ Warning: Never keep the engine idling too long during break-in. Two-stroke engines do not tolerate long-term work without loading, which can lead to the fouling of candles with soak and tailwinds.
Selection of screws and setting up of lower unit
The efficiency of the motor depends on the right propeller. The standard propeller that comes with the kit usually has a pitch of 9 or 10 inches, which is a compromise for the average boat. screw-step We need to adjust.
For heavy PVC boats with two passengers, it makes sense to install a smaller pitch propeller (e.g. 8 inches). This will allow the engine to unwind more easily and bring the vessel to plane faster, although the top speed may decrease slightly. Conversely, for light single walks, you can try a large pitch propeller (11 inches) to unlock the potential of the motor at high speeds.
An important parameter is also the installation of a lower unit in depth. Anti-cavitation plate should be approximately on the same level with the bottom of the boat or slightly lower ( 1-2 cm). If the engine is too deep, water resistance will increase and speed will decrease; if too small, air suction and cavitation will begin.
The ideal propeller allows the engine to reach the upper limit of recommended revs (about 5000-5200) when the boat is fully loaded and the throttle is open.
Frequent malfunctions and methods of their elimination
Despite the high reliability, the typical problems of two-stroke technology can occur during operation, most often owners face difficult start or unstable idling. 80% of the time the cause lies in the problem of running. fuel-system: pollution of the carburetor, the settling filter or the aging of fuel hoses.
Another common problem is overheating, which is often caused by a pump malfunction or clogging of cooling channels with algae and sand. Regular visual inspection of the control jet of water helps to detect the problem in time. sludge lower unit, as their wear can lead to water getting into the reductor.
To diagnose ignition problems, it's helpful to have a test candle on hand. If the main candle is wet and black, the mixture is too rich or the spark discharge is weak; if the candle is dry and white, the mixture is too poor or there is no fuel supply; Diagnostics by the color of the coar on the candle is the fastest way to understand what is going on inside the cylinder.
⚠️ Warning: If you experience a knock or squeal, immediately turn off the engine. Operating an engine with signs of mechanical failure (knocking fingers, breaking the bearing) will lead to expensive overhauls.
Frequently Asked Questions (FAQ)
Can I use the Komatsu 9.9 engine on salt water?
Yes, the motor can be operated in salt water, but after each exit, you need to thoroughly wash the cooling system with fresh water. Aggressive salt quickly destroys aluminum alloys and magnesium anodes, so regular maintenance is critical.
Which petrol is better to fill: 92nd or 95th?
The manufacturer recommends gasoline with an octane number of at least 92. the use of 95th gasoline does not provide any advantages for this type of engine, and in some cases (due to various additives) can even worsen the performance of the carburetor.
Do I need to pump gasoline for the winter?
Yes, it is recommended to make all the gasoline out of the carburetor or completely drain the fuel system if the engine is not used for more than a month. Modern gasolines can delaminate and lose properties, forming a resinous plaque inside the jellywood.
How much oil should I pour into gasoline for running?
For running and normal use, a ratio of 1:50 (20 ml of oil per 1 liter of gasoline) is used for quality synthetic oils. If mineral oil is used, the ratio can be 1:33, but modern synthetic oils are preferable.