outboard motor operation Tohatsu Not only does it require quality fuel, but it also requires regular maintenance of a transmission that takes on enormous loads when rotor-boiling, and water, sand and abrasive particles create an aggressive environment in which the engine is driven by a forceful environment. gear-knot Many watercraft owners mistakenly believe that the transmission fluid is poured “forever,” but ignoring replacement regulations inevitably leads to expensive repairs of gears and bearings.
Timely diagnosis of the lubricant state allows you to detect the ingress of water into the system long before the rust on the parts appears. gear-oil Provides the necessary viscosity film to prevent the teeth of gears from being uprooted at high speeds and impact loads. In this article, we will discuss in detail the technical requirements of the Japanese manufacturer, the volume of refueling for different series of engines and the algorithm of actions during scheduled maintenance.
Criteria for the selection of lubricant for the Tohatsu transmission
Company engineers Tohatsu They have developed strict specifications for the lubricants used in their products, and the basic standard to rely on when buying is classification. API GL-5This standard ensures that the package contains additives containing sulfur and phosphorus, which are necessary for the operation of hypoid gears, characteristic of the design of boat gearboxes.
Use of oils with a lower class, for example API GL-4 or transmission fluids for mechanical vehicle boxes, strongly discouraged, such products do not have sufficient EP resistance and can lead to accelerated wear of metal-metal contact pairs. SAE 80W-90 or SAE 90.
⚠️ Warning: Never use motor oil or ATF hydraulic fluid in the gearbox of an outboard motor. Their physical and chemical properties are not designed to work under high gear pressure, which will lead to rapid cog failure.
Original products Tohatsu often labeled as Gear Oil It's fully compliant with all factory requirements, but the market offers many high-quality products from well-known brands, such as: Mobil, Castrol or Liqui MolyThe main condition is that the label clearly indicates conformity with the standard. API GL-5 suitability for marine use, which implies the presence of anti-corrosion additives.
Refueling volumes and technical specifications
One of the keys to maintenance is to keep the fluid flowing exactly, and a lack of lubrication will lead to oil starvation of the top bearing, and excess will create excessive pressure when heated, which can squeeze out the glands. Tohatsu.
For low-power models of the series MFS and M (2-6 hp) are characterized by compact gearboxes that require minimal lubrication. The more powerful two-stroke and four-stroke motors have an enlarged crankcase where more fluid circulates to efficiently remove heat. Below is a table with indicative data for popular models.
| Motor model | Type of engine | Oil volume (ml) | Recommended viscosity |
|---|---|---|---|
| Tohatsu M2B2 / M3.5B2 | two-stroke | 115 - 120 | SAE 90 / GL-5 |
| Tohatsu MFS 5C / 6C | four-stroke | 115 - 120 | SAE 90 / GL-5 |
| Tohatsu M9.8B / M9.9B | two-stroke | 190 - 200 | SAE 90 / GL-5 |
| Tohatsu MFS 9.9B / 15B | four-stroke | 190 - 200 | SAE 90 / GL-5 |
| Tohatsu M30 / M40 | two-stroke | 350 - 380 | SAE 90 / GL-5 |
Always check the instructions for use (Owner's Manual) for your particular model, as the gearbox design may have changed in different years, the accuracy of volume measurement is critical to the durability of the unit, and if you're not sure about the data, you'd better double-check it with the official spare parts catalog.
When buying oil, take a tank with a margin. Even if you need 120 ml, a standard bottle often has a volume of 1 liter or 0.5 liter, and the residue will be needed for the topping or the next seasonal replacement.
Regulations for replacement and diagnosis of the condition of the fluid
Frequency of oil change in the gearbox Tohatsu The manufacturer recommends that the first replacement be performed after break-in (usually after 10 hours), and then every 100 hours or once a year, at the beginning or end of navigation.
Regular visual inspection prevents serious breakdowns, and each time you unscrew the bottom plug, you need to pay attention to the color and consistency of the leaking liquid, and it is normal to have the oil in a transparent amber or dark brown shade without any extraneous inclusions.
- 🌫️ Emulsion (color "coffee with milk"): indicates the ingress of water through worn gums or microcracks in the body.
- 🔩 Metal shavings: The presence of large sequins or pieces of metal indicates active wear of gears or bearings.
- 🌑 Blackening and smell of burning: a sign of overheating of the gearbox or the use of poor-quality lubricant.
If you find an emulsion, you have to stop operating the motor immediately, and the water in the gearbox causes corrosion of the steel parts and destroys the lubricating film, and in such cases, you don't just need to change the oil, you need to defect the assembly, replace the oil glands and bearings, and thoroughly wash the crankcase.
☑️ Diagnosis of oil condition
Step-by-step instructions for oil replacement
The procedure for replacing the transmission fluid is quite simple and can be performed independently by the owner of the motor with a minimum set of tools. API GL-5, a syringe for oil injection (manual or pneumatic), a set of screwdrivers or keys, a capacity for working out and rags.
The first step is to set the motor in a strictly vertical position, which will ensure the correct level of fluid in the crankcase, then clean the area around the drain plugs of dirt and algae, to prevent abrasive from entering the gearbox when unscrewing.
Sequence of action:1. Unscrew the bottom drain plug.
2. Unscrew the upper control plug (to improve the fluid flow).
3. drain the waste oil into the prepared container.
4. wash the gearbox with fresh oil or diesel (if there is an emulsion).
5. Inject new oil through the bottom hole before coming out of the top.
6. Twirl the top stopper, then the bottom stopper.
An important nuance is the injection process: the oil is always fed from the bottom up to avoid the formation of air stoppers, which can lead to oil starvation of the top of the gears.
⚠️ Warning: When twisting the plugs, don't drag them. Excessive force can break the thread in the aluminum gearbox body, requiring expensive repairs or replacement of the entire bottom of the lower unit.
Features of service after winter storage
If your outboard motor Tohatsu If you're in the winter in an unheated room or outdoors, you need to pay special attention to the condition of the gearbox before you start, and the temperature changes could cause the moisture inside the crankcase to condense, even if the oil seals are working, and in such cases, it is recommended to replace the oil regardless of its life.
Winter storage often reveals hidden defects in seals. When draining old oil after winter, carefully examine it for layering. If the oil remains transparent and has not changed color, this is a good sign. However, if you notice even the slightest signs of oxidation or changes in consistency, you better be safe.
How to properly store the engine in winter?
For ideal engine storage in winter, it is recommended to store it upright. If the motor is removed from the boat, make sure that the gearbox has oil to prevent the internal parts from corrosion from contact with air.
Checking the leakiness of the osteoils is a must-have procedure in the spring. After changing the oil, let the engine stand for 15-20 minutes, then check the level again. If the level has fallen, there is a leak somewhere, and before getting on the water you need to find and fix the cause.
Typical errors in the maintenance of the reducer
Despite the seemingly simple operation, outboard motor owners often make mistakes that can cost them the integrity of the unit. One of the most common problems is the use of poor-quality or inappropriate seals. It is recommended that copper or aluminum washers be changed on traffic jams every time you change oil.
Another mistake is ignoring the magnets at the ends of the plugs, and there are often small magnets at the ends of the screws of the drain plugs, whose job is to hold the fine metal shavings, and they need to be cleaned every time they're replaced, and if they're overgrown with shavings, they stop working efficiently, and the abrasive starts circulating around the system.
- 🚫 Oil pouring from above: leads to the formation of an air bubble in the area of operation of the gears.
- 🚫 Use of working out: old oil loses its properties and contains wear products.
- 🚫 Ignoring flushing: If another type of oil has been poured or water has been ingested, a simple replacement without washing will not have an effect.
You also don't need to save on the oil itself. transmission oil Cheap analogues can contain a less stable base, which, when heated during operation, changes its viscosity, no longer protecting rubbing fumes.
The quality of the oil and the tightness of the osteoils are two of the main factors determining the resource of the Tohatsu outboard motor gearbox: Regular replacement is cheaper than major repairs.
How often should I change the oil in the gearbox of the new Tohatsu engine?
For a new engine, the first replacement is done after running (10 motor hours), this is necessary to remove the products of the winding gears, then annually or every 100 motor hours.
Can I mix different manufacturers in a gearbox?
It's highly discouraged. Other additive packets can react chemically, resulting in precipitation and loss of lubricating properties.
What to do if a strong metal shaving is found in the oil?
It's a sign of mechanical damage, you have to open the gearbox, you have to replace the gears and the bearings, and if you run a motor with these symptoms, you'll have to jam completely.
Will the Tohatsu gearbox oil be suitable for other brands’ engines?
Yes, if the engine of another brand also requires the API GL-5 specification oil, the standards are universal for hypoid gears of outboard motors.