Choosing a hinged motor for a small boat is always about finding a balance between power, weight and budget. outboard motor up to 10 hp. It is considered the “golden mean” for owners of PVC inflatable boats with a length of 320 to 360 cm. It is in this class of power that an important legal nuance lies: engines up to 10 hp (inclusive) do not require registration in GIMS and the availability of control rights if the total power plant of the vessel does not exceed 8 kW.
But the market is oversupplied, and it can be difficult to understand the technical specifications of Chinese and Japanese brands, and in this review we will analyze current models, their reliability, efficiency and suitability for a variety of tasks, from quiet fishing to full-load glides.
It’s important to understand that a rated power of 9.8 or 9.9 hp is often a marketing ploy, and many manufacturers have a slightly lower value to formally fall into the “registration-free” category, although the physical engine can develop large traction forces. Yamaha 9.9FMHS or Tohatsu M9.8B Classic examples of motors that are de facto dozens, but de jure remain “nine”.
Choice Criteria: What to Look at Before Buying
The first thing to pay attention to is engineFor an inflatable boat, every extra kilogram is felt, especially if you have to carry the motor along the shore or load it into the trunk of a car. Modern two-stroke models weigh about 25-27 kg, whereas four-stroke models can reach 35-40 kg, which significantly affects the maneuverability and differentiation of the boat.
The second critical parameter is the type of ignition system and carburetor: the CDI electronic ignition ensures a stable start even after winter downtime, while old contact systems require regular prevention, and the presence of a forced lubrication system should also be considered: in two-stroke engines, oil is mixed with gasoline, and in four-stroke engines it is in the crankcase, which makes operation easier.
⚠️ Warning: When choosing a motor, be sure to check the length of the lower unit. Inflatable boats usually fit standard leg (S), but if you have a boat with high sides or a hard transom, you may need a long leg (L), otherwise cavitation and overheating will occur.
And don't ignore the water pump, and although many low-power motors are water-cooled, the quality of impeller rubber varies from manufacturer to manufacturer. Chinese replicas often use stiffer rubber, which wears out faster when working on sandbanks. The reliability of the cooling system directly affects the resource of the piston group.
Japanese Classics: Yamaha and Tohatsu
Japanese brands have been the undisputed market leaders for decades. Yamaha 9.9FMHS It's a benchmark of reliability that has been selling for years, and the two-stroke looped design delivers great traction at low revs, which is critical for a two-passenger plane and cargo.
The competitor is Tohatsu M9.8BTechnically, these engines are very close, as Yamaha has long ordered small capacity production from Tohatsu plants, but Tohatsu often has a more sophisticated exhaust system that reduces the risk of gas entering the cockpit of boats.
- 🇯🇵 Japanese assembly - quality assurance of materials and assembly.
- 🔧 Parts availability There are service centers in most cities.
- 💰 High liquidity The engines of these brands are sold quickly.
Four-stroke versions, such as Yamaha F9.9They are attractive for their efficiency and environmental friendliness, they consume 30-40% less fuel and do not require cooking a gasoline oil mixture, but they often weigh more than 35 kg, making them less attractive to lightweight PVC boat owners, who often carry the engine alone.
If you buy a used Japanese engine, be sure to ask the seller to demonstrate the thermostat. Warm up the engine on land (shortly!) or on water and check if the jet is coming from the control hole. Lack of jet is a sign of a clogged system or impeller failure.
Budget segment: Chinese brands and their features
Chinese manufacturers, such as Hidea, Parsun and Sea-ProIn recent years, there's been a huge leap in quality, and often inside the Chinese engine body you find the same components as the Japanese, but with less quality control at the output, and the price of these units can be one and a half to two times lower, which for many becomes a decisive factor.
The main advantage of the budget models is the rich equipment. While the basic Yamaha you pay extra for the screw and tank, the Chinese often put everything in the box, including additional candles and even oil. Hidea HD9.9 The Yamaha 9.9 is used to make it possible to use interchangeable parts.
But there are nuances: lower unit metal can corrosion faster if not treated with corrosion, and there are also complaints about the quality of plastic casings and the reliability of lower unit compounds. Resource Chinese engines are comparable to Japanese counterparts, but require more careful attention from the first hours of operation.
⚠️ Warning: When running a Chinese engine, strictly observe the proportion of oil in the mixture (usually 1:25 for the first 10 hours).
An interesting solution for thrifty water engines is to buy a 9.9 hp engine that is structurally 15 hp. Removing the power limiter (often just replacing the petal valve or reconfiguring the carburetor) allows you to get an increase in speed, but legally you will operate an unregistered powerful vessel, which may cause questions from inspectors.
Comparative table of specifications of popular models
To make it easier to choose, we have brought the key technical parameters of the market leaders into a single table, and note the difference in weight and volume of the tank, as these parameters directly affect the comfort of operation.
| Model | Type of engine | Weight (kg) | Tank volume (l) | Brand country |
|---|---|---|---|---|
| Yamaha 9.9FMHS | two-stroke | 27.0 | 12 | Japan |
| Tohatsu M9.8B | two-stroke | 26.5 | 12 | Japan |
| Mercury 9.9M | two-stroke | 27.0 | 12 | United States/Japan |
| Hidea HD9.9 | two-stroke | 28.5 | 12 | China |
| Yamaha F9.9 | four-stroke | 35.0 | 12 | Japan |
Why are the weights of motors different?
The difference in weight can be caused by the use of different aluminum alloys for the lower unit, the thickness of the lower unit pipe or the design of the flywheel. The heavier motor is often more stable on the wave, but more difficult to transport.
Four-stroke or two-stroke: the eternal argument
Choice between 2T and 4T If your goal is to get to the fishing point quickly, catch the fish and return, the two-stroke will be perfect. It is lighter, faster and easier to transport (you can carry on the side, although not recommended).
Four-stroke engines (4TThey're good at long walks and trolling, they're quieter, which is important for sound sounding sound and comfort, and 4T engines don't require constant oil purchases and mixing, which eliminates the dirty work on the shore.
- 🚀 Dynamics Two-strokes are better at accelerating the boat.
- 🔇 Noise Four-strokes work much quieter.
- ⛽ Expenditure 4T is 20-30% more economical.
In terms of reliability, the modern two-stroke Yamaha and Tohatsu are almost as good as four-strokes. The 4T's main enemy is oil that needs to be changed, and the risk of hydraulic shock if it is not properly preserved for the winter. In 2T engines, lubrication is constant, which protects parts but requires quality oil.
☑️ What to check before starting a new engine
Running and first launch: important nuances
Proper running is key to a long engine life. Regardless of price and brand, new rubbing parts should get used to each other. For two-stroke engines, the standard break-in mode is 10 minutes idling, then 10 hours of operation with periodic changes in speed, not exceeding 50-60% of the maximum.
Four-stroke engines require oil change after the first 2-5 hours of motors, during which time metal shavings from rubbing parts get into the oil, and if not drained, it will work as an abrasive. Don't neglect this rule, even if the instructions say "oil is filled for full term" - this is often marketing.
When you first start, make sure that the control hole is a confident stream of water. Working "dry" even for a minute can lead to deformation of the cylinder head and expensive repairs. Temperature conditions It should be controlled visually or by touch (the body should be warm but not scorching).
⚠️ Warning: Never start a motor without a water pump submerged in water, even for a few seconds. Using buckets or barrels for a "test" start often results in air sucking and instantaneous overheating.
High-quality break-in increases the life of the engine by 30-40%. Don't chase power in the first 10 hours of operation - let the engine "diverge" gradually.
Frequently Asked Questions (FAQ)
Do I need to register the engine 9.9 hp in GIMS?
Under current Russian law, small vessels with engines above 8 kW (approximately 10.88 hp) are subject to registration. 9.9 hp (7.3 kW) motors do not formally require registration if the total power of all engines on the boat does not exceed this threshold.
What is the best gasoline to use for a motor?
For most modern engines (2010 and later) recommended gasoline AI-95. the use of AI-92 is possible only if it is explicitly stated in the instructions, but can lead to detonation and loss of power. Gasoline must be fresh, the shelf life of gasoline with ethanol-additives does not exceed 1 month.
Can the motor be kept upright?
Two-stroke motors can be stored vertically on a lower unit (as in operation) or horizontally on a specific side (in the instructions, usually on the carburetor side). Four-stroke motors are stored strictly vertically so that oil does not enter the combustion chamber through the valve. 4T motor can only be tilted briefly for transportation.
Why does the engine stop at high speeds?
The main reasons: clogging of the fuel filter, violation of the ventilation of the fuel tank (the valve is clogged in the lid), problems with the ignition system (coil or CDI) or air pumping through the gasket of the carburetor, it is also worth checking the condition of the spark plug.