Choosing a power unit for a small inflatable or metal boat is always a compromise between power, weight and cost. 9.9 horsepower This figure is not accidental: it allows you to operate a boat without registration with the GIMS and without the need to obtain a license to operate a small vessel, if the total weight of the boat is less than 200 kg.
But behind this “unregistered” figure lies the huge potential available to owners, and most current models are technically capable of developing significantly higher traction while remaining reliable and economical. Two-stroke and four-stroke These engines have their own design features that directly affect the choice of the end user, and understanding these nuances will help to avoid mistakes when buying.
In this article, we will discuss in detail why this particular class of motors is so popular, how to properly run a new unit and what you need to know about the possibility of increasing power.
Why 9.9 HP is the most popular class of motors
The popularity of engines of this power is primarily due to legislative restrictions: according to current regulations, to drive a boat with an engine up to 9.9 hp (inclusive) and a total weight of a complex up to 200 kg, registration is not required in the register of small craft, which saves owners from annual payment of state duty and undergoing a technical inspection.
In addition to the legal aspects, this class of engines offers the optimal weight-to-thrust ratio. For inflatable boats from 3.2 to 4.0 meters long, this engine is the ideal balancerom. It can bring the planing mode even a loaded PVC boat, providing a speed of about 25-30 km / h, which is enough for fishing or cruising.
And it's also important to note the economics, because the fuel consumption of these units is minimal, so you can spend the whole day on the water with a full tank. Two-stroke models They consume about 3-4 liters per hour at full speeds, while four-stroke analogues are even more economical on small strokes.
⚠️ Warning: When buying a boat and an engine, always add up their weight. If the boat weighs 110 kg and the engine weighs 27 kg, you are already (close) to the 200 kg limit, not including the weight of fuel, battery and equipment.
There is also a misconception (a common misconception) that 9.9 forces are not enough for serious tasks, and in practice, this motor confidently pulls a water skier (one person) and copes with moderate wind and excitement. Low-speed traction Such engines are often higher than those of more powerful counterparts, due to the peculiarities of the gear ratio of the gearbox.
Two-stroke or four-stroke: what to choose
The question of choice 2T and 4T Two-stroke engines are traditionally 5 to 10 kg lighter than their four-stroke counterparts, which is critical for carrying the motor to the water by hand, they are less sensitive to boat roll and can operate in any position, which is important when fishing in overgrown water bodies.
Four-stroke engines, by contrast, are quieter, more economical at low speeds, and do not require mixing oil with gasoline. single-turnBut their weight and more complex construction often discourage small boat owners.
For fishing, where you need to change position often and pull the engine to the shore, a two-stroke is often more practical. For family walks and long walks on calm water, the four-stroke will provide greater comfort due to low noise levels.
The cost of service should also be taken into account. Repair of two-stroke enginesFour-stroke units require regular oil change in the crankcase and more careful handling when transporting (only on a certain side or vertically).
Technical specifications and capabilities of tuning
Many buyers are unaware that the 9.9 hp motors are often physically identical to the 15 hp models from the same manufacturer, the only difference being that there is a restrictive washer in the carburetor or a software restriction in the control unit (ECU), which allows for a legal increase in power by removing the restriction, although this puts the boat into the register category.
The main technical parameters that should be considered when choosing:
- 🚀 Engine capacity: It is usually 169 cc for 2T and about 200-210 cc for 4T in this class.
- ⚙️ Transfer ratio of gearbox: affects the thrust; for heavy boats it is better to choose models with traction gearboxes.
- 🔋 Ignition system: Electronic CDI or TCI provides stable start-up and operation.
- 💧 Cooling: Water (flowing) is the standard, but the quality of the water pump is important.
The process of decoding the motor (removing the restriction) is simple, but requires technical knowledge. In two-stroke Yamaha or Tohatsu models, it is often enough to replace the petal valve or remove the washer. In modern four-strokes, you may need to flash the control unit.
⚠️ Attention: Removing power restrictions makes it illegal to operate a boat without registering with the GIMS. You risk getting fines and detention of the vessel when checking documents.
How do you technically remove the restriction?
In two-stroke motors, the restriction is often implemented through a valve in the carburetor or the shape of a petal valve. In four-stroke motors, it is programmatically via the ECU. Physical intervention takes 15 minutes to 2 hours depending on the model.
When choosing, you should also pay attention to the presence of electric starterFor 9.9 hp engines, this is an option that makes life much easier, especially for women or the elderly, but it adds weight (battery and starter) and reduces reliability due to the complexity of the system.
Comparison of popular models: Tohatsu, Yamaha, Honda
The market offers many brands, but the leaders in this segment are traditionally Japanese manufacturers. Tohatsu often acts as an OEM for other brands (for example, Mercury), which indicates the high quality of their engines.
Yamaha is famous for its reliability and availability in any region, and its engines are easily repaired even in the field. Honda relies on the sustainability and quietness of four-stroke models, but they are usually more expensive.
Below is a comparative table of popular models, which will help to orient in the specifications:
| Model | Type | Weight (kg) | Workload (cm3) | Features |
|---|---|---|---|---|
| Tohatsu M9.8B | 2T | 26.0 | 169 | Legendary reliability, easily tuned |
| Yamaha 9.9GMHS | 2T | 27.5 | 169 | High liquidity in the secondary market |
| Honda BF10D | 4T | 39.0 | 222 | Quiet operation, OHV system |
| Suzuki DF9.9B | 4T | 38.0 | 284 | Digital ignition, economy |
When buying Chinese analogues (Hidea, Sea-Pro, Mikatsu) you should be prepared for the fact that the real power may differ from the declared, and the quality of the metal of the lower unit may be lower.
When buying a used motor, be sure to ask the seller to start it on water. Working "dry" even for 30 seconds can lead to overheating and jamming of the piston group.
Rules of running and first start
The life of the engine depends on the quality of the break-in, neglecting this stage leads to cylinder bullying and loss of compression in the first seasons, and breaking in is necessary for grinding the parts of the piston group and bearings.
The break-in process takes about 10 hours. In the first hours, you can not give full gas. It is recommended to work at speeds up to 50% of the maximum, periodically raising them to 70-80% for a short time, but not fixing the throttle in one position for a long time.
For two-stroke engines during break-in, some manufacturers recommend slightly increasing the oil share (e.g. 1:40 instead of 1:50), although modern semi-synthetic oils allow you to follow standard instructions.
☑️ Checklist before first launch
After the first 2-3 tanks, be sure to replace them. transmission oil In the process of grinding the gears, metal shavings can get into the oil, which must be removed.
Typical malfunctions and their elimination
Even reliable 9.9 hp engines can cause problems when used improperly, and overheating is a common problem, caused by debris entering the intake or by the wear of the pump impeller. Control jet There should always be water, and its absence is a signal to stop immediately.
Start problems are often related to fuel quality or spark plugs. In Russian conditions, it is recommended to use NGK or Denso candles and change them every 2 seasons.
If the engine develops full speed, but the boat does not go, the problem may be in the slashed-up propellerIt's a safety mechanism that saves the gearbox when it hits an obstacle. Always have a spare set of veneers and screws on board.
⚠️ Warning: Never attempt to straighten a bent propeller with a hammer. A misbalancing will cause a strong vibration that will destroy the lower unit and crankshaft bearings.
You can use a strobescope to diagnose ignition problems, or you can just visually check the spark by twisting a candle, but remember that a quality spark does not guarantee the correct angle of ignition ahead.
Tips for Winter Storage and Conservation
Proper preservation for the winter extends the life of the engine for years, and the main rule is to completely drain the water from the cooling system, to do this, the motor is left in an upright position or pushed the system with compressed air.
The fuel system needs to be fully developed or preserved with a fuel stabilizer, and the gasoline left in the carburetor for the winter evaporates, leaving a resinous plaque that clogs the jellyfish.
It is recommended to treat the outer surfaces of the motor with anti-corrosion lubricant and store it in a dry room, preferably in an upright position. For two-stroke motors, it is useful to make a "gassing" with an increased proportion of oil before storage to preserve the cylinder from the inside.
Quality preservation for the winter takes no more than 30 minutes, but saves hundreds of dollars on repairs of the carburetor and cylinder-piston group in the spring.
Compliance with these simple rules will allow your engine 9.9 hp to serve faithfully for many years, delighting with a stable start and confident running in any weather.
Frequently Asked Questions (FAQ)
Can I refuel the engine 9.9 hp AI-92 gasoline?
Yes, most modern outboard motors, especially two-stroke and four-stroke electronically ignition engines, are designed for gasoline with an octane number of at least 92. However, using the AI-95 can slightly reduce the risk of detonation and the formation of soot, especially in hot weather.
How many liters per hour does the engine consume 9.9 hp?
The consumption depends on the load and type of motor. Two-stroke engine at full gas consumes about 3.5-4.5 liters per hour. In trolling mode (3000 rpm), the flow drops to 1.5-2 liters. Four-stroke analogues are more economical by 15-20%.
Do I need to register the engine 9.9 hp in GIMS?
The engine itself, with a capacity of 9.9 hp (or less), is not subject to registration, but a small vessel is subject to registration if its mass in running order with the engine exceeds 200 kg. If your boat is light, then the entire set is not required to register.
What kind of oil to use into the motor gearbox?
The gearbox is filled with a special transmission oil for outboard motors (usually labeled as Gear Oil or Hypoid Gear Oil). It is important that the oil has additives that prevent emulsification when water enters. The oil volume in the gearbox of the engine 9.9 hp is usually 300-350 ml.