Choosing an outboard motor for a small boat or boat is always about finding a balance between power, weight and reliability. Johnson's outboard motor 20 The two-stroke classic from the American brand that became part of Evinrude Corporation has proven itself for decades as a workhorse for fishermen and water lovers.
This unit attracts attention for its simplicity of design, making it an ideal candidate for self-service even in garage conditions. Despite the fact that modern four-stroke counterparts are quieter and more economical, it is the 20-horsepower Johnson that remains the standard of maintainability. Many owners value it for its ability to run on fuel of the lowest quality, which is often found in remote water bodies.
In this article, we will discuss in detail the technical nuances of operation, typical malfunctions and secrets of correct configuration. Johnson 20 hpUnderstanding how this engine works will allow you to extend its lifespan significantly and avoid costly repairs in the midst of navigation, and we'll look at everything from oil selection to ignition angle adjustment.
Technical specifications and design features
The heart of the unit is a two-cylinder internal combustion engine, operating on a two-stroke cycle. The design provides loop blowing of cylinders, which ensures a sufficiently efficient combustion of the mixture with a minimum number of moving parts. Power of 20 horsepower is achieved at revolutions of about 5000-5500 per minute, which is the optimal indicator for planing light inflatable boats and small aluminum "kazak".
The cooling system deserves special attention: the centrifugal water pump located in lower unit provides the circulation of off-shore water through the engine shirt. The pump-pumping doe It's made of rubber, and it's a consumable that needs to be replaced regularly, and the bottom editor is designed to work in overgrown water, although cut-off studs are still present on most models.
Secrets of Model Marking
Knowing the model code, you can pinpoint the year of release and the country of assembly, and the code is usually stamped on the screw hub or on the mounting bracket, for example, the letters "J" at the beginning indicate Johnson, and the subsequent numbers and letters indicate a specific modification and the year of production.
The weight of the engine in running order is approximately 40-45 kilograms, which makes it relatively easy to transport it in the trunk of a passenger car. cylinder-diameter They're designed to give you maximum torque at low rpm, which is critical when you're trolling or going against the current.
- 🔹 Engine type: two-stroke, 2 cylinders, inline
- 🔹 Working volume: 362 cc (standard for most models 20 hp)
- 🔹 ignition system: CDI (electronic contactless)
- 🔹 Recommended fuel: AI-92 with oil in a ratio of 1:50 (for modern oils)
Power supply system and carburetor setting
The stability of the engine depends on the quality of the preparation of the fuel-air mixture. Johnson 20 It is usually a single-chamber or two-chamber float type unit, depending on the year of manufacture, the main adjustment elements are the screws of quality and quantity of the idle mixture, as well as the position of the throttle.
A frequent problem for owners is unstable idling or dips when a gas is opened abruptly, which often indicates the need to clean the jelly or replace the gaskets. Ignoring symptoms It can cause the piston group to overheat due to the impoverishment of the mixture. For accurate diagnosis, you need to use a tachometer, since the adjustment "by ear" does not always give an objective result.
The tuning process requires a consistent approach: first, the engine is warmed to operating temperature, then the quality screw achieves maximum speed stability, after which the number screw sets the minimum necessary for operation without load.
⚠️ Attention: Before any adjustment of the carburetor, make sure that the intake manifold is tight. Suction of air through cracks in the manifold or the crankshaft coils makes any settings meaningless and dangerous for the engine.
Maintenance regulations (TO)
The durability of an outboard motor depends not so much on the brand as on the discipline of the owner in matters of maintenance. Johnson 20 hp There is a clear schedule, divided into seasonal and annual procedures, and neglecting bearing lubrication or replacing fuel filters is a direct route to major repairs.
Every 50 hours or at the end of the season, complete defects must be carried out. Particular attention should be paid to the condition of the lower unit shaft and the ointments that prevent water from entering the gearbox. Regular lubrication of slash joints and checking the tightening of the engine mount bolts to the transom are also mandatory.
☑️ Seasonal engine maintenance
The table below shows the main service intervals for key engine units, and meeting these deadlines ensures that the engine starts on the first time at the beginning of the next season.
| The knot/aggregate | Action. | Interval (motoclock) | Interval (time) |
|---|---|---|---|
| Redder oil | Replacement | 100 | 1 time per year |
| Ignition plugs | Cleaning/Replacement | 50 / 100 | Seasonally. |
| Fuel filter | Replacement | 100 | 1 time per year |
| The pump-pumping doe | Visual examination | 50 | Every season. |
| Bearings | Lubricant | 100 | 1 time per year |
Typical malfunctions and methods of their elimination
Even the most reliable machine is subject to wear. Johnson 20 They're the ones who are most likely to have problems with the ignition system and the fuel system, and if the engine stops working at full speed or stops working under load, they're going to check the candle caps and the high-voltage wires first, and contact oxidation is a scourge of any kind of technology.
Another common problem is overheating. If you notice that water stopped coming from the control hole, or if you notice signs of overheating (a change in the color of the paint), immediately turn off the engine. Most often, a sand-filled cooling system or a collapsed pump impeller is to blame. Operating the engine without cooling even for 2-3 minutes leads to pistons being bullied.
When storing the outboard motor in the off-season, be sure to treat the internal cavities of the cylinders with conservatory oil. To do this, turn the candles, pour 10-15 ml of oil into each cylinder and slowly turn the crankshaft with a starter several times (without candles).
Knocking at the bottom of the motor may indicate the development of rod bearings or the entry of a foreign object into the screw. the diagnosis of knocking is carried out by listening through a technical pipe or a long screw applied to the ear. Metal thumping on idles, disappearing when gas is added, often indicates the need to adjust the carburetor or replace the needle bearing of the rod.
⚠️ Warning: Never attempt to start a motor with the screw removed without loading on water or in a barrel at high speeds. This can lead to the rods turning and engine destruction due to lack of water resistance.
The choice of propeller and its impact on the specifications
The propeller is a transformer of engine power into traction. Johnson 20 The standard is a propeller with a pitch of about 9-10 inches and a diameter of 9.25 inches. However, the choice of the optimal propeller depends on the type of boat, its load and operating conditions.
If the propeller is too big a pitch, the engine will not be able to reach operating speeds (5000-5500 rpm) in overload mode, which leads to coking candles, overheating and increased fuel consumption, and vice versa, too small a step will lead to "spread" of the engine when it exceeds the maximum allowable revolutions, which is fraught with the destruction of the piston group.
When you look at the screw, pay attention to the edges of the blades. Even small holes and burrs reduce efficiency and create cavitation bubbles that destroy the metal. Aluminum screws They are easy to handle but require precision, whereas stainless steel holds geometry better but costs significantly more.
- 🔸 The screw step affects the maximum speed and acceleration
- 🔸 The diameter of the screw determines the thrust at low speeds
- 🔸 Number of blades (usually 3) affects smoothness
- 🔸 Material (aluminum/steel) affects durability and price
Preparation for winter storage and conservation
Proper conservation is the key to ensuring that you don't have to spend your budget on repairs in the spring. The main enemy of the engine in winter is moisture residue and oxidation. After the last trip of the season, the engine must be completely free of water. To do this, it must be left upright until the water drains out of the cooling system.
The fuel system also needs to be prepared, and the best way to do this is to extract the fuel residue from the carburetor, let the engine stall on its own, or use a fuel stabilizer if there's still a mixture in the tank. Rust inside the carburetor The oxidation of old gasoline is one of the main reasons for problems with starting in the spring.
The main rule of wintering: the motor should be stored in a dry, ventilated room, strictly in a vertical position to avoid deformation of the osteoils and water entering the cylinders.
The outer surfaces should be cleared of salt deposits (if the operation was at sea) and covered with a special lubricant or silicone spray. Remember to remove the battery if you use an electric starter and recharge it once a month. The mechanical part also requires attention: the screw slits are abundantly lubricated, and it is advisable to cover the lower unit with a dust cover.
These simple but important rules will help you Johnson 20 This motor is designed to work, but it requires respect for its design and understanding of the processes that take place inside, and investing time in maintenance always pays off with reliable water work.
Which oil is best used for Johnson 20: mineral or synthetic?
Johnson 20 engines produced after the 1990s are recommended to use semi-synthetic or fully synthetic oils labeled TC-W3. They provide better lubrication at high loads, smoke less and hardly form soak on candles and pistons. Mineral oils are only permissible for very old models and require more frequent replacement and mixing ratios of 1:25 or 1:40, while synthetics allow for a 1:50 or 1:100 cast depending on the oil manufacturer.
Why does the engine stop when the valve is opened?
If the Johnson 20 is idling but dies when you add gas, the problem is the medium- and high-speed fuel supply system, the main causes are clogged carburetor main jet latch, the fuel pump (membrane) is faulty, the air pump through the crankshaft or intake manifold, and a contaminated fuel filter-sulphant.
Can Johnson 20 be used in seawater?
Yes, but with a mandatory freshwater wash after each use, seawater is aggressive against aluminum alloys and magnesium anodes, the owner must regularly check the condition of the tread anodes on the lower unit and change them when corrosion is more than 50%. Ignoring the wash will lead to rapid failure of the cooling pump and corrosion of the exhaust system.
What kind of spark plugs are required for Johnson 20?
Standard candles for most Johnson 20 hp models are marked NGK BR7ES or Champion RN7YC. The gap between the electrodes should be 0.7-0.8 mm. The use of candles with the wrong potassium number can lead to detonation (too hot) or oiling and skipping sparks (too cold) candles.