Choosing a reliable power unit for a small vessel is always associated with a compromise between power, weight and economy. Tohatsu outboard motor 40 two-stroke It has been widely considered a benchmark in its class for many years, and the Japanese School of Engineering has built an incredible safety margin that is highly valued by both professional water-engineers and avid fishermen.
Unlike today's four-stroke models, this model offers higher power specifications per kilogram of weight. For owners of inflatable floaters and light aluminum boats, this is a critical parameter that affects driving performance and handling. In this article, we will discuss in detail the design features, nuances of operation and hidden advantages of the design. Tohatsu M40D2.
Many users mistakenly believe that two-stroke technology has irrevocably become a thing of the past, giving way to environmentally friendly 4T engines. two-stroke The simplicity of the design, the absence of a complex lubrication system of the crankcase and the possibility of long-term operation at high speeds make this unit indispensable for certain operating conditions.
Design features and reliability of the engine
The heart of the unit is a single-cylinder or two-cylinder unit (depending on the specific modification of the year of release), made with a minimum number of moving parts. Piston group It is made of high-quality aluminum alloys that have undergone special heat treatment, which allows the engine to withstand tremendous heat loads without the risk of cylinder bullying, which often happens in lesser-known competitors.
The cylinder blowing system deserves special attention. Tohatsu We've used an improved deflex or loop purge scheme to minimize the loss of the working mixture. torque It's available at almost the lowest rpm, providing a steady way to planing even when the boat is fully loaded. Unlike its Chinese counterparts, there are no backlashes in the gearshift system, and the reverse mechanism is smooth.
⚠️ Note: When running a new engine, strictly follow the instructions for the proportion of the mixture. Using a poor mixture in the first hours of operation can lead to irreversible damage to the piston group, which is not a guarantee case.
The engine Carter is made of magnesium alloy, which reduces the overall weight, but requires careful treatment during transportation. Corrosion It's not scary because it's multi-stage corrosion-resistant, all the internal and external surfaces, and even after the season of active salt water, the motor keeps its tidy look if you wash the cooling system with fresh water in a timely manner.
Technical specifications and productivity
Considering technicalThe engine develops 40 hp at a weight that often does not exceed 50-55 kg (depending on the length of the daydwoot), which makes it one of the lightest in the 40-stroke class. For comparison, four-stroke analogues can weigh 15-20 kg more, which significantly affects the differentiation of the boat.
Ignition system CDI Capacitor Discharge Ignition provides stable sparking under all conditions, whether it's a cold start in the early morning or a high speed in the heat, ignition timing is automatically selected, which eliminates detonation and ensures smooth engine operation. Below is a table with the main specifications of the model.
| Parameter | Meaning | Note |
|---|---|---|
| Power | 40 hp (29.4 kW) | At 5,500 rpm |
| Workload | 696 cm | 2 cylinders |
| Lubrication system | Premix. | Mixing with petrol |
| Weight (short leg) | ~52 kg | No fuel, no fuel. |
| Fuel tank | 25 l (standard) | It is possible to install an external |
An important aspect is the cooling system. Forced water pump With rubber impellers, heat is removed efficiently even when driving at low speeds. The pump design makes it easy to replace worn elements without removing the entire motor. The impellers' life when used in clean water is 200-300 hours.
Use only high-quality two-stroke oils labeled TC-W3. Cheap oils can form soda on candles and in exhaust windows, reducing engine power.
Fuel consumption and efficiency of operation
The question of the economy of two-stroke engines is often controversial. Indeed, classic carburetor engines burn some of the mixture into the atmosphere. Mikuni carburettors, which are fixed on Tohatsu 40At cruising speeds (about 4000-4500 revolutions), fuel consumption is approximately 12-14 liters per hour, which is comparable to some lower-power four-strokes.
The savings are achieved not only due to the design of the carburetor, but also due to the absence of mechanical losses on the rotation of the oil pump and valve mechanism characteristic of the 4T. Engine efficiency If properly tuned and used with quality AI-92 or AI-95 gasoline, the engine runs steadily without requiring frequent adjustment of the composition of the mixture.
The cost of ownership is not just the price of a liter of gasoline: Two-stroke engines require less maintenance costs. The lack of an oil crankcase means you don't have to buy expensive four-stroke oil and filters. The gearbox oil is replaced once a season or every 100 motor hours, which is significantly cheaper than maintaining a complex 4T system.
The secret to fuel economy
Customizing the carburetor to a "poor" mixture can reduce consumption, but will lead to overheating. Optimal mode is a slightly enriched mixture at full revs, which ensures cooling and maximum power.
Launch system and control
Motor control is traditionally carried out through squirt (a gas pen on the tiller) or through the remote panel (D-box), if the model provides such a possibility. For the 40-horsepower version, the presence of remote control is almost necessary, since the force on the tiller can be significant, especially when maneuvering against the wind.
The engine can be started manually (starter cord) or by an electric starter. Modifications with an electric starter are equipped with a more powerful lighting coil (12V, 6A or higher), which allows you to connect navigation lights, sonars and GPS trackers without installing an additional battery. Battery battery It must be securely secured and protected from splashes.
The gearshift mechanism (forward-neutral-back) is designed with a rotating ramper or a separate lever, the switching progress is clear, with a characteristic click confirming the gear is on, which eliminates situations where the backlash causes the transmission to fly under load. Tohatsu It is famous for its reliable launch lock system in gear, which prevents a sharp start of the boat.
☑️ Checking before getting on the water
Maintenance and typical faults
Despite the legendary reliability, Tohatsu 40 outboard motor The most common problem that owners face is clogging of the fuel system. Carburetor's Jeeklers are very sensitive to the quality of gasoline and the presence of water in the tank. It is recommended to regularly unscrew the float chamber's drain screw to remove condensation.
The second important component is the ignition system, and candles should be checked every 50 hours, and candles can tell you about the state of the engine: black soda indicates a rich mixture or an excess of oil, white indicates a dangerous overheating. Candle gap must strictly comply with the specification (usually 0.8-0.9 mm), otherwise ignition gaps are possible.
⚠️ Warning: Never keep a full tank of gasoline in winter, the fuel loses its properties and forms resinous deposits that clog the carburetor, drain the fuel or use a stabilizer.
The gearbox requires oil change and an emulsion check, if the oil is "coffee with milk", then the sealing of the ossels is impaired, and the engine with water trapped in the gearbox will quickly corrosion the gears and bearings. Salmon It is better to change preventively once in 3-4 seasons of active operation.
Comparison with competitors and model selection
In the market of used and new engines Tohatsu 40 There are direct competitors like the Yamaha 40X and Suzuki DT40. Yamaha is often praised for traction but scolded for noise and vibration. Suzuki is robust, but its ignition system can be more moody to moisture. Tohatsu In this trio occupies a niche of the "golden mean", offering a balance between the silence of work (due to the high-quality balancing of the crankshaft) and maintainability.
When choosing between a new and used model, you need to consider the reciprocating life. Japanese engines in the 90s and early 2000s, with proper care, run 1,500+ hours to the first capital. However, finding a live one becomes more difficult. New engines have no wear problems, but they cost much more. Two-stroke engine It is often more profitable to buy, knowing its history, than to take a cheap Chinese analogue.
The important criterion is the availability of spare parts. Tohatsu In the CIS, parts are easier to find than rare models of other brands. Pistons, gaskets, glands and carburetors are often interchangeable between 30, 40 and 50 hp models, which makes it easier to repair in the field, making the engine an excellent choice for remote expeditions.
Tohatsu 40 hp is an investment in reliability, and the high residual value in the aftermarket allows the engine to be sold in a few years for almost the same money it was bought for.
FAQ: Frequently asked questions
What is the best gasoline for Tohatsu 40?
It is recommended to use unleaded gasoline with an octane number of at least 92 (AI-92); the use of gasoline with an octane number of 95 is permissible, but does not give an increase in power, but only reduces the risk of detonation; the main thing is the freshness of the fuel and the absence of alcohol additives (ethanol, methanol), which can dissolve the rubber elements of the carburetor.
Is this engine smoking too much?
With proper running and quality oil (TC-W3), the smoke is minimal and only noticeable when the valve is opened sharply. Older engines or engines with an incorrectly tuned carburetor can smoke more. After warming up at idle speeds, the exhaust should be almost transparent.
Can this motor be used in salt water?
Yeah, Tohatsu M40 It has a corrosion-resistant coating designed for use in seawater, but after each outing, the cooling system must be thoroughly washed with fresh water and the external moving parts (tilt hinges, thrust) must be lubricated with a consistent lubricant.
What is the maximum speed of a boat with this engine?
Speed depends on the type of boat and load. For an inflatable boat with a length of 3.6-3.8 meters with one driver, the speed will be 35-40 km / h For a light aluminum boat (for example, "Crimea" or "Salute") from 40 hp you can accelerate to 45-50 km / h On heavy boats, the engine will work in a gentle mode, providing a comfortable cruise.