Choosing a outboard motor for a small inflatable boat or a light aluminum boat often comes down to finding the middle ground. Yamaha 8bhp engine.The sleeve has become a benchmark for reliability and efficiency for thousands of anglers and water enthusiasts, and this power allows you to confidently glid a boat with a length of 3 to 4 meters with one or two passengers on board, while ensuring comfortable speed and maneuverability.
Unlike more powerful analogues, the eight horsepower unit does not require a driver’s license to drive a vessel in most CIS countries, making it attractive for beginners. Yamaha It offers a wide range of modifications, ranging from lightweight two-stroke versions to four-stroke electronically ignitioned quieter vehicles, and understanding the differences between these models is critical before buying, as it affects not only the price but also the further maintenance costs.
In this article, we will discuss in detail the technical features, hidden nuances of operation and real fuel consumption figures. You will learn why this power range is considered the most popular in its class and what parameters should be paid close attention to when choosing a used or new unit.
Model range and technical differences
The range of engines with a capacity of 8 horsepower from the Japanese manufacturer is represented by several key modifications, each of which is sharpened for specific tasks.two-stroke) and four-stroke (four-strokeTwo-stroke models such as the classic Yamaha 8AThey are less weighted and simpler in design, making them ideal for transport in the trunk of a passenger car.
Four-stroke options, for example Yamaha F8A or F8CMHThey're more complex engineering, and they have a full-fledged crankcase lubrication system that eliminates the need to mix gasoline with oil, which not only makes it easier to refuel, but also significantly reduces noise and vibration, and reduces exhaust gas, which is especially important for fishing, where silence is key.
It's important to note the differences in the control system. EH or CMH They are often equipped with an electric starter, which is a huge plus for women or older people, while the manually run versions are also available.T) require physical effort, but gain weight. electric starter manual start often becomes a decisive factor in the configuration of the boat complex.
When buying a used motor, be sure to check the compression. For a serviceable two-stroke Yamaha 8 hp, the value in the range of 9-11 kgf / cm2 is considered normal.
Advantages of four-stroke technology
The transition to a four-stroke cycle of the engine opens up new comfort opportunities for the owner. Yamaha F8 It works much quieter than two-strokes, which allows you to talk on the go without raising your voice, and not having to constantly add oil to gasoline and wait for the mixture to mix, saves time and nerves before each step on the water.
The sustainability of four-strokes is not just a marketing ploy, they burn cleaner, they don't burn with gasoline, they circulate in a closed loop. exhaust They do not have a characteristic gray smoke and a sharp smell, which is highly appreciated by the surrounding on the pond and the passengers of the boat themselves.
⚠️ Attention: Despite the oil filter and lubrication system, in four-stroke engines, it is critical to check the oil level with a probe regularly before each start.
The four-stroke engine is typically more powerful, thanks to fewer engine speeds at the same boat speed and a more gentle temperature regime, but it pays a lot of weight: a four-stroke can be 10-15 kg heavier than a two-stroke, which is important to consider if you plan to carry the motor on your shoulder often.
Fuel consumption and economy
One of the most common questions that potential buyers ask is about the appetite of the engine. fuel The Yamaha 8 hp engine is directly dependent on the mode of operation and loading of the boat. At idle speeds, when driving against the current or when trolling, consumption is minimal and can be less than 1 liter per hour.
When the engine is running at full capacity, the numbers go up. Four-stroke models show better fuel efficiency due to a more complete combustion of the mixture. Two-stroke versions are characterized by higher consumption, especially if the carburetor is not tuned or old spark plugs are used.
Below is a comparative table of fuel consumption for different operating modes (data averaged for a single-driver PVC boat):
| Mode of work | Turnover (rpm) | Consumption (l/hour) 2T | Consumption (l/hour) 4T |
|---|---|---|---|
| Idle move | 1000-1500 | 0.6 - 0.8 | 0.4 - 0.6 |
| trolling | 2500-3000 | 1.5 - 2.0 | 1.2 - 1.6 |
| Full gas (plane) | 5000-5500 | 3.0 - 3.5 | 2.2 - 2.8 |
The four-stroke engine pays off its higher initial cost for 2-3 seasons of active operation due to savings on gasoline and oil.
The actual consumption can vary depending on the fuel quality, the condition of the propeller and the cleanness of the bottom of the boat. Use of gasoline with an octane number below the recommended (usually an AI-92 or an AI-95) can lead to detonation and increased consumption.
Maintenance and maintenance
Durability of the motor Yamaha The basic regulation requires changing the oil in the gearbox after the first 10 hours (break-in) and then every 100 hours or once a season, ignoring this rule can lead to water getting into the gearbox and expensive repairs of gears.
The cooling system also requires attention. You need to check the control stream of water regularly, and if the jet becomes weak or disappears, this is a signal that the water channels are clogged or the pump impeller wears out. Impeller replacement A procedure that an experienced owner can perform on their own with a minimum set of tools.
☑️ Seasonal engine maintenance
Fuel filters and carburetors are critical for two-stroke engines. Modern gasolines often contain ethanol, which can aggressively affect rubber seals and carburetor membranes during prolonged downtime, so if you leave the boat for the winter, it is recommended to either produce all the gasoline from the float chamber or use special fuel stabilizers.
⚠️ Warning: Never keep the engine in the propeller or side position without draining the oil if the specific model instruction prohibits it, which can lead to oil leaking into the cylinder and hydraulic shock on the next start.
Tuning and modernization: screws and not only
The standard propeller, which comes with the 8 hp Yamaha engine, is chosen as an average option. However, to achieve maximum speed performance or improve traction at full load, often requires a replacement of the propeller. The main parameter here is the screw pitch. Increased pitch will allow you to develop more speed in straight sections, but will steal the acceleration dynamics.
For lightweight boats and full-load fishing (boat + motor + 2 people + equipment), it is often recommended to put screws with a smaller pitch than the regular one. This will allow the engine to bring the vessel to planing faster and feel more confident on the wave. Solas or Michigan WheelThey offer a wide range of aluminum and composite screws.
Effect of screw material on speed
Aluminum screws are cheaper and easier to repair when hitting rocks, but they tend to bend, changing the geometry of the blades. Stainless steel is stronger and thinner, which gives a speed gain of 3-5%, but such a screw can transfer energy to lower unit when hit, damaging the gearbox.
In addition to the screws, owners often install door-wheel