Choosing an outboard motor for a small boat or boat often comes down to finding the optimal balance between power, weight and cost of operation. Yamaha engine 20 It has been a leader for decades, and the 346 cubic centimeter two-stroke design has proven itself to be a benchmark for reliability in harsh environments.
This unit is ideal for PVC inflatable boats from 3 to 4 meters in length, as well as lightweight aluminum "kazak", it is often chosen by anglers who care about the speed of sleeving, and hunters who appreciate the simplicity of construction. Yamaha 20 It provides sufficient thrust for confident movement against the current and wind.
In this article, we will discuss in detail the technical nuances, features of carburetor configuration, typical malfunctions and secrets of extending the life of this popular engine. You will learn why it is still relevant and what to look for when buying a used copy.
Technical specifications and design features
The basis of the power unit is a time-tested two-stroke scheme with loop purge. Power of 20 horsepower It's achieved at 5,000-5,500 rpm, and the cylinder capacity is 346 cm3, which is the standard for this class, and it's important to note that there's a CDI ignition system that provides a stable spark even when the battery is discharged or when the starter starts.
The water-type cooling system (pump) effectively removes heat, but requires clean water intakes. The engine weight as standard is about 44-45 kg, making it relatively easy to carry by two people or to be mounted on a transom by one person with the ability to do so. Yamaha 20 It has one gear (forward/neutral/back), which simplifies the design of the gearbox.
The carburetor system of Mikuni or Keihin (depending on the year of production and the market) requires periodic adjustment. The fuel mixture is prepared in a ratio of 1:50 when using quality oil for two-stroke engines.
| Parameter | Meaning |
|---|---|
| Type of engine | two-stroke, 2-cylinder |
| Workload | 346 cm |
| Maximum power | 20 hp (14.7 kW) |
| Ignition system | CDI (electronic) |
| Recommended fuel | AI-92/95 + butter 2T |
⚠️ Attention: Using pure gasoline without adding two-stroke oil will cause the pistons to jam instantly and the engine to fail. Always mix the mixture thoroughly in a separate container before pouring into the tank.
Fuel consumption and efficiency of operation
One of the main questions that owners worry about is how much they eat. Yamaha engine 20In full gas (WOT) mode, the flow rate can reach 7-8 liters per hour, but in practice such modes are rarely used. For cruising speeds of about 70-80% of the maximum, consumption is reduced to 4-5 liters.
At low speeds, when trolling or moving in displacement mode, the flow rate drops to 2-3 liters per hour. This makes the engine economical enough for cruising use. However, it is worth remembering that two-stroke engines inherently are less economical than four-stroke analogues due to the loss of part of the fuel mixture through the exhaust window.
The economy directly depends on the quality of the prepared mixture and the condition of the carburetor. Yamaha 20 It is sensitive to impoverishment of the mixture, which can cause overheating.
Maintenance and routines
Resource Yamaha 20 engine The simplicity of the design allows you to do most of the work yourself in garage conditions, basic maintenance includes candle replacement, compression check and lubrication of the knots.
Every 50-100 hours, it is recommended to remove the top cover and blow the engine with compressed air, removing dust and algae from the cooling zone. Particular attention should be paid to the state of the lower unit lubricant in the gearbox - it should not have a milky hue, which indicates water ingress.
☑️ Checklist of seasonal services
Lubrication of all points specified in the manual should be made by a special water-resistant lubricant. Yamaha 20 has several syringes: gear shift thrust, throttle axis and other movable elements.
Typical malfunctions and methods of their elimination
Despite the reliability, Yamaha engine 20 It's not without the characteristic diseases, and most often, owners have problems with their ignition system or carburetor, and they may stall at high speeds or not develop full power.
One common problem is the destruction of the crankshaft glands, where the motor starts to suck air, which leads to impoverishment of the mixture and overheating of the piston group, and often the CDI sensor or ignition coil fails, especially if the tightness of the hood space is disturbed.
⚠️ Attention: If the engine suddenly stalls and stops starting, don't spin the starter indefinitely. First check for sparks and candles. Prolonged scrolling of the flooded engine can lead to a hydraulic shock.
Symptoms of CDI malfunction
If there is a spark, but it is weak or disappears when heated, most likely the problem in the switching unit, and also a sign of a CDI malfunction can be the inability to reach revolutions above 3000-4000 per minute, even if the carburetor is set perfectly.
Customization of the carburetor and the quality of the mixture
Proper tuning of the carburetor is the key to a long life Yamaha 20Factory setting is usually optimal, but over time or with a different quality of fuel, adjustment may be required.
The sign of a poor mixture is white soak on candles, overheating and the screeching of a piston, a sign of a rich mixture is black soak, smoky exhaust and loss of power. Yamaha's 20 engine It is better to tolerate a slightly enriched mixture than a depleted one.
When setting the carburetor, twist the mixture quality screw very slowly, at 1/8 revolution, waiting for the engine reaction. A sharp change in the position of the screw can cause the engine to stop.
The tuning process is better done by ear and by the tachometer, if it is connected, the optimal position is considered when the engine is stable on idles and smoothly gains speed without dips.
Comparison with competitors and modifications
In the used motor market Yamaha engine 20 The Japanese build Yamaha is distinguished by its casting quality and corrosion resistance. However, Suzuki often wins in traction at the bottom, and Tohatsu is famous for its indestructibility.
There are various modifications Yamaha 20: rumpled, distance-setting, long and short leg. There are screw-protected versions for shallow water, but the classic 20 most often has a standard lower unit.
The main advantage of Yamaha 20 over competitors is the highest liquidity in the secondary market and the availability of spare parts in any region.
Advice on choosing a used copy
When buying used Yamaha 20 engine First of all, look at the compression. It should be in the 9-11 atmospheres and the same in both cylinders. A difference of more than 1 atmosphere indicates wear of the piston group or the occurrence of the rings.
Make sure you ask the seller to start the engine on water. Evaluate the water pressure from the control hole, it should be a confident stream. Check the thermostat: hot water should also come from the control hole on the heated motor.
Check the lower unit for backlashes. Rock the screw, there shouldn't be backlash. Also check the lower unit lubricant, if it's light and thick, great, if it's dark or emulsified, the gearbox needs repair.
Which octane is best for the Yamaha 20?
The optimal fuel is AI-92 gasoline. AI-95 is allowed, but does not provide advantages, and in some cases (with poor-quality fuel) can lead to a more rigid engine operation.
How often should you change the oil in the gearbox?
The gearbox oil is recommended to be changed once a season or every 100 motor hours. When operating in salt water, it is better to reduce the interval to 50 hours. Use only specialized transmission oil for outboard motors (usually API class GL-4 or GL-5 with appropriate tolerances).
Can I store the Yamaha 20 motor vertically?
Short-term storage in a vertical position (on the screw) is permissible, but not recommended for a long period (wintering). For long-term storage, it is better to use a special stand or bracket to keep the oil glass in the crankcase, rather than remaining in the cylinders or gearbox, creating a load on the glands.