Selecting a power unit for a small vessel is always a complex engineering and economic equation that directly affects the comfort and safety of navigation. In the mid-capacity segment, where a confident full-load plane is required, the Tohatsu 40 hp outboard motor has established itself as a benchmark for reliability and unpretentiousness. The Japanese engineering school that underpins these engines guarantees the highest build quality and durability of the units even in extreme operating conditions.
Many owners of boating technology agree that it is the 40-horsepower modification that is the “golden mean” for PVC boats with a length of 3.8 to 4.5 meters and light aluminum boats. Power range It allows you to easily take the boat to the plane, while providing sufficient thrust reserve for towing a skier or passing areas with a strong oncoming current. Unlike weaker analogues, this engine does not "choke" on the wave and keeps the speed stable.
However, buying this level of equipment requires a deep understanding of the technical nuances to avoid costly mistakes when choosing between two-stroke and four-stroke versions. Tohatsu It offers solutions that can vary dramatically in their design, although they carry the same power label.
Technical specifications and design features
The foundation of productivity of any Tohatsu M40 The two-stroke versions are high power and lighter, which is critical for inflatable vessels, where every extra kilogram affects driving performance. The four-stroke versions, in turn, offer efficiency and environmental friendliness, but require a more complex lubrication system and often have an increased mass.
The cooling system, implemented on the principle of off-shore water intake, works extremely efficiently due to the thought-out geometry of the water pump. impeller The engine is made of wear-resistant rubber that can withstand fine sand and silt, although operating in such conditions still reduces the resource of the unit. The thermostatic valve ensures that the engine warms up quickly to operating temperature, after which the circulation of antifreeze (in this case, water) becomes complete.
Particularly noteworthy is the Capacitor Discharge Ignition (CDI), which requires no adjustment of gaps and is characterized by high stability of spark formation. Even with a sharp change in load or water entering candle wells, the engine continues to work smoothly, without dips and trinium. Carburetor versions are equipped with aperture carburetors that maintain efficiency when the boat rolls up to 45 degrees.
⚠️ Warning: When you first start or after a long downtime, be sure to check for water in the control hole ("urinal"). The absence of a jet more than 10-15 seconds at idle turns can lead to overheating and jamming of the piston group.
The weight specifications of the models vary depending on the type of engine and the length of the daydwoot. For the standard version, the weight is about 72-78 kg, which requires the use of reinforced transes or special mounts when installed on light boats. Elongated lower unit (L) adds a few more kilograms, but is necessary for boats with high transom or specific bottom geometry.
Two-stroke or four-stroke: the eternal dispute of owners
The choice between the 2T and 4T versions of the 40 hp Tohatsu engine is often the subject of fierce debate in fishing communities. Two-stroke engines are traditionally prized for their “sharpness” and ability to react instantly to the handle of gas. They are lighter than four-stroke counterparts by about 15-20%, which for a PVC boat can be a decisive factor when pulling a boat ashore alone.
On the other hand, four-stroke engines are much quieter and do not require the preparation of a fuel mixture. No need to mix gasoline with oil makes it easier to refuel and reduces the risk of an error that could fatally affect the life of a two-stroke. Fuel consumption 4T versions are lower by 20-30%, which with long-term standalone outputs turns into a significant budget savings.
The four-stroke engines are lower in vibre load, which has a positive effect on the life of the engine mounting elements and passenger comfort. However, they are more sensitive to roll and can not work for long in the upside-down position, which is sometimes necessary when overcoming shallow water or thickets. Tohatsu In this respect, they are more versatile and forgive many mistakes of inexperienced boatmasters.
The secret of the hybrid regime
Many owners of two-stroke engines use a special oil for running in a ratio of 1:50 even after the completion of routine work, which allows you to extend the life of the crankshaft oal and reduce the nagaroprostivovovoznoy on candles, although the manufacturer specifies different standards.
Cost of maintenance also plays a role: the four-stroke requires regular replacement of motor oil in the crankcase, an oil filter and has a more complex cylinder head with valves. The two-stroke is structurally simpler, but requires quality oil for the mixture and regular cleaning of exhaust windows from the soak during heavy operation.
Fuel consumption and economic efficiency
The efficiency of the outboard motor is a parameter that directly affects the range of the trip without refueling. For a 40 hp model, fuel consumption is highly dependent on the mode of operation and type of engine. At idle, the four-stroke version consumes about 0.6-0.8 liters per hour, while the two-stroke version can “eat” up to 1.2 liters even without loading.
When driving in planing mode (about 5000-5500 rpm), the difference becomes even more noticeable: a four-stroke engine will show a flow rate of about 12-14 liters per hour, while a two-stroke counterpart is able to consume 18-22 liters under similar conditions. Savings almost 10 liters per motor hour with active operation for the season, it results in tens of thousands of rubles.
However, two-stroke engines often use a mixture where the oil ratio is 1:50 or 1:100 (for modern oils), which means that a full tank of gasoline (25 liters) will require you to add only 250-500 ml of oil, which has a slight impact on the total cost of the motor hour, but is critical for lubrication.
| Mode of work | Turnover (rpm) | Consumption 2T (L/h) | 4T consumption (L/h) |
|---|---|---|---|
| Idle move | 800-1000 | 1.0 - 1.2 | 0.6 - 0.8 |
| Economy cruise | 3000-3500 | 8.0 - 9.0 | 5.5 - 6.5 |
| Full gas (plane) | 5500-6000 | 18.0 - 22.0 | 12.0 - 14.0 |
| Maximum traction | 6500+ | 24.0+ | 16.0+ |
To increase the range, many experienced water-engineers recommend using larger tanks or carrying canisters, especially when planning multi-day expeditions. Fuel filter in this case, it should be in perfect condition to eliminate the risk of water or dirt from additional containers in the food system.
⚠️ Note: The use of gasoline with an octane number below the AI-92 (for example, AI-80) is strongly not recommended for Tohatsu engines. This can cause detonation, overheating and destruction of the piston group, which is not a warranty case.
Maintenance and regular maintenance
The durability of the Tohatsu 40 outboard motor depends on the owner’s discipline in maintenance matters. The Regulation provides for the replacement of the oil in the gearbox after the first 20 hours (break-in), and then every 100 hours or once a season.
Ignition plugs require inspection and cleaning of the scent every 50-100 hours. Tohatsu 40 Usually used candles NGK BR7HS or analogues, the gap on which must be strictly adjusted within 0.9-1.0 mm. breach of the gap leads to unstable operation at idle speeds and difficult start.
☑️ Seasonal engine maintenance
The two-stroke lubrication system requires only quality oils labeled TC-W3. Saving on oil or using workouts leads to tailpipes and compression drops. Four-stroke versions require engine oil and filter replacement strictly according to the manual.
Preservation for winter is a critical step: you need to drain the water completely from the cooling system, blow out the carburetors and treat the internal cavities with aerosol lubrication (fog), and you need to keep the engine upright to avoid deformation of the crankshaft glands.
When storing the engine in winter, it is recommended to remove the candle and pour 5-10 ml of engine oil into the cylinder, after which slowly turn the crankshaft with a starter several times, this will create a protective film on the cylinder mirror and prevent corrosion.
Typical malfunctions and methods of their elimination
Despite its high reliability, the Tohatsu 40 outboard motor, like any mechanism, can malfunction. One of the most common problems is the difficulty in starting or not having a spark. In 80% of cases, the cause lies in spark plugs that have failed or are covered with carbon, or in violation of the gap between the magneto and the coil.
Overheating of the engine often signals a malfunction of the water pump. impeller You might lose elasticity or roll into the shaft by stopping pumping water, and you might want to check the thermostat that might have stuck in the closed position, and the cooling pipes for cracks or blockages.
Carburetation problems, such as floating revs or dips in a sharp opening of the throttle, are usually associated with contamination of the jelly or air sucking through the gaskets, which requires disassembly and ultrasonic cleaning of the carburetor, as well as replacement of the remix of the gaskets.
⚠️ Warning: If the engine suddenly stalls and doesn't start, don't try to spin it with the starter indefinitely. First, check for spark and fuel. Torsion with the starter with the candles flooded can lead to hydraulic shock and serious damage to the rod.
Knocking at the bottom of the daydwoot may indicate wear of gear gears or propeller bearings, and operation of the motor with this symptom is prohibited, as it can lead to the destruction of the gearbox body and loss of the propeller in the water.
Selection of propeller and tuning of productivity
Proper propeller selection is key to unlocking the potential of the Tohatsu 40 engine. Factory propellers often have averaged specifications that may not match your boat's weight and swimming style. The main parameter is the pitch of the propeller, which affects top speed and thrust.
If the engine does not develop maximum speeds (less than 5000-5500 rpm at full gas), then the screw is too heavy (big step) and the engine is running in overload mode. If the revolutions exceed 6000, the screw is too light, and you do not use all the power, and you risk torsioning the engine.
The optimal propeller allows the engine to achieve maximum passport speeds when the boat is fully loaded, ensuring the best acceleration and maximum speed without overloading.
For heavy boats or towing, it makes sense to install a screw with a reduced pitch (for example, 9 instead of 11). This will increase traction at the bottom and make it easier to go to the plane, although the maximum speed may decrease slightly. Aluminum screws are cheaper, but steel (stainless steel) are stronger and have thinner blades, which increases efficiency.
Installing a hydraulic lift on a lower unit can significantly improve driving performance, especially on flat-bottom boats, which stabilizes wave travel, reduces yaw and allows earlier plane, saving up to 10-15% of fuel.
Owner reviews and summary
Analyzing the experience of thousands of owners, the Tohatsu 40 outboard motor is the leader in its class in terms of price/quality. Users note its “unkillability”, the ability to start half-around even after winter idleness and excellent traction, many call it a “workhorse” that will not let you down far from civilization.
The downsides are often the noise of the two-stroke versions and the relatively high fuel consumption compared to modern four-strokes made in China, although the reliability of the Japanese unit often outweighs these drawbacks. Four-stroke models are praised for their silence, but criticized for their weight and complexity of service in the field.
In conclusion, Tohatsu 40 It's a choice for those who value predictability and reliability, a motor that forgives many operating errors, but requires respect for maintenance, and when properly maintained, it can work thousands of hours of motorcycling, giving the owner the joy of communicating with water.
What is the best gasoline for Tohatsu 40?
The manufacturer recommends using unleaded gasoline with an octane number of at least 92 (research method) or 87 (motor) in Russia, the optimal choice is the AI-92 or AI-95 from proven gas stations. Using the AI-80 will lead to detonation, and the AI-98 will not give advantages, but may be too heavy for carburetor versions.
How often should you change the oil in the gearbox?
The first oil change in the gearbox is made after running (the first 20 hours) to remove the metal shavings. Then the replacement is made every 100 hours or once a year, regardless of the mileage. If an emulsion is detected, the change is required immediately to find the cause of the water ingress.
Can I store the Tohatsu 40 motor horizontally?
Long-term storage (more than a few days) in a horizontal position is not recommended, especially for four-stroke versions, as oil can leak into the combustion chamber or valve. Two-stroke motors are more tolerant, but they are better stored vertically or on a special stand to avoid deformation of the glands and leakage of fuel residues.
Why does the engine smoke blue smoke?
Blue smoke is a sign of oil burning. In a two-stroke engine, it's normal if the smoke is not excessively thick and there is no loss of power. If the smoke is black, the mixture is too rich (a lot of gasoline), if white (steam) water enters the cooling system. In a four-stroke engine, blue smoke indicates wear of oil rings or oil entering the combustion chamber.