In the world of compact water vehicles, it is Johnson 3.5 outboard motor It's a model that, despite its age and conservative design, is still in demand among anglers and small boat enthusiasts, and the two-stroke powerplant is simple, almost primitive, but it's a trait that keeps it alive in the field.
Many owners choose Johnson 3.5 It's a great tool for its ability to work on almost any mixture of fuel and oil, although it's not worth abusing it. The light weight of the design allows you to transport the unit in the trunk of a car or even in a large backpack, making it ideal for hunting in hard-to-reach places. In this article, we will discuss in detail the technical nuances, features of service and real capabilities of this "baby".
It should be noted immediately that 3.5 horsepower is a threshold for many countries, allowing you to operate the engine without mandatory registration in the GIMSThis makes life much easier for owners of inflatable boats and small boats, eliminating bureaucracy, but in order for the engine to last, you need to understand the principles of its operation and maintenance requirements.
Technical specifications and design features
The design of the engine is based on a time-tested two-stroke scheme with one cylinder. Workload The engine is 49 cubic centimeters, which at certain speeds gives the declared power. The ignition system here is classic, contact fly (CMB), which means there is no complex electronics that could fail from moisture or vibration.
Cooling is done by off-shore water through a water pump system located in lower unit. It is an effective method, but it requires constant cleaning of the water intakes from algae and debris. The body is made of light alloys and covered with corrosion-resistant protective enamel, although salt water still requires careful washing after each use.
An important element is the lower unit, which can have different lengths depending on the modification (S, L, XL). Inflatable boats are usually suitable standard leg, and for keel motorboats may require an elongated version.
⚠️ Warning: When installing the motor on a transom, make sure that the lower unit is submerged in water to a sufficient depth. Dry pump operation, even for a few seconds, can lead to overheating and deformation of the impeller.
Below is a table of the main technical parameters that will help you compare this model with modern analogues:
| Parameter | Meaning |
|---|---|
| Type of engine | two-stroke, 1 cylinder |
| Power | 3.5 hp (2.6 kW) |
| Cylinder volume | 49 cc. |
| Ignition system | Magdino (CMB) |
| Weight (no fuel) | 13.6 kg |
Fuel system and mixture preparation
Since Johnson 3.5 It's a two-stroke engine, it doesn't have a separate crankcase lubrication system like the four-stroke ones, all the rubbing parts are lubricated with oil dissolved in gasoline, so the quality of the fuel mix is critical to the durability of the engine, and it uses gasoline with an octane number of at least AI-92.
Mixing requires the use of special two-stroke oils for water technology (marked TC-W3), the mixing ratio is usually 1:50 for new engines and break-in units, but for older models or when operating at full speed in hot weather, the proportion is sometimes increased to 1:40 for better lubrication.
The mixing process must take place in a separate clean canister, not directly in the engine tank. First, a portion of the gasoline is poured, then the calculated amount of oil is added, the mixture is shaken, and only then the remaining gasoline is added, which ensures an even distribution of the oil film.
It is not recommended to store the finished mixture for more than one month, since gasoline loses its properties, and oil can precipitate. If the engine is planned to stand idle in the winter, the fuel system is better to develop dry or canned.
Start-up and break-in of the new engine
Launch The Johnson 3.5 outboard motor Before pulling the cord, make sure that the motor is fixed to the transom, the lower unit is submerged in water (or a hose with water is supplied), and the gear switch is in a neutral position, the gas lever (curve or tiller) should be in the "Start" position or slightly open.
After a few swings with the primer (if there is one in a particular modification) or just waiting for the fuel to arrive, a sharp jerk of the cord is made. The motor must grab and go idle. Warming usually takes 2-3 minutes, after which you can start driving.
Particular attention should be paid to the procedure of running in if you have purchased a new or refurbished engine. Running in is necessary for grinding the piston group and bearings. In the first hours of operation, you can not give full gas. It is recommended to develop 3-5 fuel tanks in a gentle mode, varying the speed from 30% to 70% of the maximum.
☑️ Checklist before first launch
During the break-in, the tightness of all connections and the absence of vibrations, which may indicate improper assembly or balancing, are also checked. If the motor is running smoothly, without dips and smoke beyond normal, the procedure can be considered successful.
Adjustment and adjustment of the carburetor
Carburetor in Johnson 3.5 It's usually membrane-type, which allows the engine to operate at any angle of inclination, which is critical for outboard motors. However, over time, you may need to adjust the quality and quantity of the mixture, and the screws are set up on the carburetor body, but access to these can be limited by the casing.
Before adjusting, the engine must be warmed to operating temperature. The mix quality screw ("L" for low revs) is set up at idle, and the "H" screw (high revs) is set up under load or at maximum revs. The factory setting is usually optimal, and you should not climb there without needing.
Signs of misconfiguring are: unstable idling, stalled when adding gas motor, overheating or, conversely, black smoke from the exhaust. Black smoke and soak on the candle speak of a “rich” mixture (a lot of oil / gasoline), and white soak and overheating – of “poor”.
⚠️ Warning: Poor mixture (low fuel, plenty of air) is dangerous for the piston group. Prolonged work on the distilled mixture can lead to burnout of the piston and bullying in the cylinder in minutes.
If simple adjustment of the screws does not help, it may be clogged jelly or damaged membrane, which requires removal and defective carburetor, cleaning with ultrasound or replacement of the remplekt.
Typical malfunctions and methods of their elimination
Even the most reliable Johnson 3.5 outboard motor It can fail. Most often, the problem is with the ignition system or the fuel supply system. If the engine doesn't start, the first thing you need to do is check for a spark. To do this, you twist the candle, you stick it with a thread to the mass of the engine and you pull the starter. The spark should be bright, blue and skip between the electrodes.
The second common problem is the lack of fuel supply, which can be caused by clogging of the sediment filter, which is in the tank or in the carburetor itself, and also often "blown" petal valves at the inlet, especially if the engine has been idle for a long time, they can be gently washed with gasoline or replaced.
Compression problems are less common, but are possible during long-term use. Wear of piston rings leads to power drops and difficult start. You can check the compression with a compressometer screwed in instead of a candle. For two-stroke 3.5 hp compression in the area of 8-10 atmospheres is considered normal.
What do I do if the spark is gone?
If the spark is gone, check the integrity of the high-voltage wire and cap. Often oxidized contacts under the flywheel (interrupt contacts), they can be cleaned with a topfill or fine sandpaper, and also check the gap between contacts when open (usually 0.35-0.4 mm). If the contacts are whole, it is possible that the ignition coil will break.
The vibration of the motor can be caused not only by poor balancing, but also by damage to the lower unit or hitting a foreign object in the screw. Always check the screw for chips and cracks, as an unbalanced screw will quickly "kill" the lower unit bearings.
Seasonal storage and conservation
Proper conservation Johnson 3.5 The first thing you need to do is to make the residue of the carburetor fuel mix, let the engine run until it stops, and that will prevent the chicklers and membranes from evaporating the lighter fractions of the gasoline.
Then you have to change the oil in the gearbox, even if the time is not yet up, water that gets into the gearbox through the glands when cooling can freeze and break the body or damage the gears, the spark plug needs to be twisted out, drop some engine oil into the cylinder and turn the crankshaft several times, then wrap the candle back.
Store the engine better in a vertical position, in a dry room, covered from dust. It is not recommended to store the unit in a hermetically closed box or bag, since condensate formed during temperature changes will cause corrosion.
Lubricate all outer metal surfaces and cables with a thin layer of conservation lubricant or WD-40 before wintering – this will protect them from oxidation in a wet garage.
In spring, before installing on the boat, be sure to inspect the lower unit for cracks and check the condition of the glands, and be sure to check the condition of the fuel hoses, which during the winter could become rigid and crack.
Comparison with analogues and final conclusions
In his class. Johnson 3.5 It competes with models such as the Tohatsu M3.5, Yamaha 3CM or Mercury 3.3. Johnson’s main advantage is the maintainability and availability of parts, which are often interchangeable with other engines manufactured by OMC (Evinrude).
However, in terms of noise and vibration, it can be inferior to more modern developments. Fuel consumption is also higher than that of four-stroke competitors, but with such a low power, the difference in liters is not so critical for the owner's wallet.
When you choose this engine, you get a workhorse that forgives many of the mistakes of beginners. It is not afraid of bad gasoline (within reasonable limits) and can be easily repaired in garage conditions. For fishing on small rivers, lakes or for use as a spare engine on a yacht, this is one of the best options for price/quality ratio.
Johnson 3.5 is the pragmatic choice that needs maximum reliability and maintainability, not record-breaking efficiency or quietness.
So in conclusion, if you take care of it properly, it can last for decades, going from father to son, and the key is to be mindful of the proper mix and keep an eye on the cooling system.
Frequently Asked Questions (FAQ)
What is the best gasoline for Johnson 3.5?
It is recommended to use un-leaved gasoline with an octane number of 92 (AI-92). Gasoline with a higher octane number (95, 98) can be used, but it is not advisable, since the degree of compression of the engine does not require this, the main thing is the freshness of the fuel and the lack of water in the tank.
Can this motor be used in salt water?
Yes, you can, but after each outing, the motor must be thoroughly washed with fresh water, salt deposits quickly corrode aluminum alloys and disable the cooling pump, and it is also advisable to use motors with anti-corrosion coating of anodes, if they are designed.
Why does the engine stop when the gas is opened?
Most often this indicates clogging of high-speed jellyplate in the carburetor, water entering the fuel tank or violation of the tightness of the fuel hoses (air sucker), also the reason may be incorrectly exposed gap of the contacts of the interrupter.
Do I need to register a boat with a 3.5 hp engine?
Under current Russian legislation, registration with GIMS is subject to small vessels weighing up to 200 kg inclusive, equipped with an engine capacity of more than 8 kW (10.88 hp). Since 3.5 hp is about 2.6 kW, registration of the engine itself is not required. However, if the weight of the boat with equipment exceeds 200 kg, registration will have to be carried out, regardless of the engine power.
Where to find spare parts for old Johnson models?
Parts can be found in specialized boating stores, at disassemblies or ordered through online stores specializing in old engines, many of which are unified with Evinrude engines of the same year.