outboard motor Tohatsu 9.8 It is deservedly considered one of the most reliable "workhorses" on domestic water bodies, but even such time-tested equipment requires regular and competent maintenance. The heart of the lower part of the unit is a gearbox, which experiences tremendous stress when transferring rotation from the engine to the propeller, and it is the quality of the lubrication in this unit that determines the durability of the entire structure. Many owners mistakenly believe that it is enough to add fluid as the level decreases, but the systematic replacement of the transmission oil is a critical procedure, ignoring which can lead to expensive repair of gears and bearings.
In this article, we will discuss in detail, butter You need to use a specific model Tohatsu M9.8How to properly carry out the replacement procedure yourself without contacting the service and what nuances should be paid close attention. The correct selection of lubricating composition directly affects the reduction of friction, heat removal and protection of metal surfaces from corrosion, especially given the aggressive aqueous environment in which the motor operates.
Before you start practical actions, you need to clearly understand that gearbox oils are divided into different classes of viscosity and chemical composition, and the use of the wrong product can be fatal for the unit. Owners often confuse motor and transmission fluids, which is categorically unacceptable, because the use of the wrong product can be fatal for the unit. additiveism Here we'll look at the manufacturer's specifications and the algorithm that allows you to service the bottom of the motor yourself.
Manufacturer requirements and oil specifications
Company engineers Tohatsu They have developed clear specifications for the lubricants used in their motor gearboxes, and a 9.8 horsepower model is no exception. API GL-4 or API GL-5These standards ensure that the necessary anti-sharp additives are available to withstand the high pressure in the contact spot of the gear teeth.
It is important to note that modern synthetic and semi-synthetic formulations have significantly better specifications than mineral counterparts, especially when working in extreme temperature regimes. Viscosity of oil It plays a key role: too thick liquid at low temperatures can create resistance, and too liquid when heated will lose its protective properties. Tohatsu The best choice is considered products with viscosity SAE 90 or SAE 80W-90.
⚠️ Never use motor oil or automatic transmission (ATF) fluids in the outboard motor gearbox, as they do not have the necessary metal adhesion and are quickly washed out by water.
When choosing a product, pay attention to the presence of special emulsifying additives that allow the oil to temporarily mix with water in the case of microscopic leaks, forming an emulsion that does not block the operation of the unit until the moment of maintenance. However, you can not rely on this property constantly - the main task of the oil remains to create a durable one. lubricant The manufacturer's brand also matters: the original oils. Tohatsu It is guaranteed to meet all requirements, but high-quality analogues from the Mobil, Shell or Liqui Moly They also do a great job of doing the job.
When buying oil, pay attention to the date of production: the shelf life of transmission oils is usually 3-5 years, after which additives can begin to precipitate.
Tools required and preparation for replacement
Oil replacement procedure in the gearbox Tohatsu 9.8 It's technically simple and doesn't require complex equipment, but having the right tool will make the job quick and clean. You'll need a set of wrenches or heads to unscrew the plum plugs and bay plugs, which are located on the engine's lower unit. Also, a special syringe for pumping oil, because it's almost impossible to fill the gearbox from the bottom up by accident because of the design of the channels.
In addition to the main tool, prepare a tank for the waste liquid, which may contain metal shavings and wear products. sealer (pads) for drain plugs, because old aluminum or copper rings deform after the first use and may not ensure leakproofness during re-installing. Cleanliness in the process is key to success, so stock up on rags and degreaser to wipe the area around the traffic jams.
- 🛠️ Keyset (usually 10 mm or 12 mm size, depending on the year of issue)
- 💉 Syringe for transmission oil (manual or pneumatic)
- 🧽 Brake cleaner and rags to remove dirt
- 🔩 New sealing rings (gassing) for traffic jams
Before starting work, the motor must be placed upright so that the oil glass is in the bottom of the gearbox. If the motor is in operation, let it cool down so that it does not get burns, but it is better to change the oil on a warm unit, rather than a cold one, since the warm liquid has less viscosity and drains more easily. Make sure that the motor is clean around and foreign objects cannot fall into the open holes of the gearbox.
☑️ Preparation for oil replacement
Step-by-step instructions for oil replacement
The replacement process begins with the removal of the bottom drain plug, through which the waste material is removed. Tohatsu 9.8 There are two holes, the top (fill) and the bottom (drain), and you need to unscrew the plugs in this sequence: first the bottom, then the top, to ensure normal fluid flow and air output, and be prepared for the fact that you will leak out black or dark brown liquid, which is a normal sign of the presence of wear products.
After the old oil has been drained, the gearbox should be thoroughly washed if there is a suspicion of emulsion or dirt. You can use a small amount of fresh oil or a special wash liquid to wash it through the cavities. Then the nose of the syringe with new oil is inserted into the bottom hole, and the injection process begins. The oil should be fed slowly, watching the upper hole: once the liquid starts to flow out of the upper hole, this is a signal that the gearbox is completely filled and the air is displaced.
⚠️ Attention: You need to twist the upper plug without removing the syringe from the lower hole so that when removing the spout of the syringe, the oil level does not fall below the critical mark.
The final step is to install new sealing rings and twist the plugs. The timing of the tightening should be moderate: you should not make excessive efforts not to break the thread or deform new gaskets. Enough tighten the plug to the end and slightly press the key. After the procedure, wipe the lower unit clean and start the engine for a few minutes at idle speeds in a container of water to make sure there are no leaks.
The main secret of successful replacement is filling the gearbox from the bottom up until the oil appears in the upper hole, which guarantees the absence of air traffic jams.
Diagnosis of the state of the oil and reducer
Fused oil can tell a lot about the technical condition of your body. Tohatsu 9.8And a careful analysis of its color and consistency helps prevent serious breakdowns. Normally, the workout is dark, almost black, but it retains a uniform structure without visible inclusions. If you notice shiny particles in the liquid that look like aluminum powder or large chips, it is an alarm signal indicating active wear and tear. gear or bearings.
Particular attention is required when the oil acquires a light coffee or cream hue, which indicates that water enters the gearbox. Water can penetrate through the glands of the shafts, especially if the motor was operated in salt water or the glands have exhausted their resource. The presence of water in the oil dramatically reduces its lubricating properties and leads to corrosion of internal parts, so when detecting an emulsion, it is needed not only to replace the oil, but also to find the cause of depressurization.
| Color/State | Reason. | Action |
|---|---|---|
| Black, homogeneous. | Normal wear and tear | Planned replacement |
| Coffee colored (emulsion) | Water intrusion | Replacement of gums, flushing |
| Silver gloss (aluminum) | Wear of the shell or pistons | Defection of the gearbox |
| Large steel shavings | Wear of gears/bearings | Urgent repair of the checkpoint |
If you find large metal fragments during the drain, further operation of the engine without repair is strictly prohibited, as this can lead to a jamming of the gearbox and a break in the lower unit. In such cases, a complete dismantling of the unit, defective friction pairs and replacement of damaged elements is required. Regular visual monitoring of the oil condition allows you to identify the problem at an early stage, when repair will cost minimal costs.
Why are magnets on traffic jams important?
Inside the drain plugs, magnets are often installed to hold the fine metal shavings, keeping them from circulating through the gearbox and working like an abrasive. Clean the magnets with each replacement.
Frequency of maintenance and seasonal storage
How often to change the oil in the gearbox Tohatsu 9.8The manufacturer recommends the first replacement after break-in (the first 10 hours of operation), and then every 100 hours or once a year, whichever comes first. However, heavy operation in heavy conditions (sand, silt, frequent impacts on the bottom) may require more frequent maintenance.
Special attention should be paid to preparing the engine for winter storage. Many experts advise changing the oil in the gearbox just before preservation for the winter, so that the knot does not remain working with wear products and possible impurities of water that can cause corrosion during the winter. Fresh oil will create a protective film on the parts and ensure a calm start next season.
- 📅 First replacement: after 10 hours (break-in)
- 📅 Scheduled replacement: every 100 hours or once a season
- 📅 Winter storage: Replacement with fresh oil is required
- 📅 Emergency replacement: when water is hit or screws are struck
If the engine is idle for a long time, it is recommended to periodically (once a month) turn the screw manually so that the lubricant is distributed to the details, although with the right oil, this is not a strict necessity.
Common errors in service
Despite the simple procedure, the owners Tohatsu 9.8 They often make mistakes that can nullify all maintenance efforts, and one of the most common problems is using inappropriate seals, and some people try to seal the plugs with silicone sealant instead of installing new metal rings, which leads to difficulties in the next dismantling and the risk of getting the sealant inside the gearbox.
Another mistake is to ignore the oil level. As mentioned, the level should go to the bottom edge of the upper hole. If the oil is smaller, the upper bearings and gears will remain greaseless, working dry, which will lead to their rapid overheating and destruction. Conversely, excess oil can create excessive pressure when heated and squeeze out the glands.
⚠️ Warning: Do not try to top the oil through the top hole without removing the bottom stopper - you will not be able to control the level and will guarantee an air plug inside the crankcase.
It is also worth mentioning the misconception that “oil is poured in there forever.” The gearbox is not 100% hermetic in the long run: temperature expansions, vibrations and aging of the osteoils lead to natural renewal and loss of lubrication properties. Neglecting oil replacement is a direct route to overhauling the bottom of the engine, which can cost up to 50% of the price of a new lower unit.
The use of original sealing rings and oil level compliance are two factors that account for 90% of the success of a long life.
Frequently Asked Questions (FAQ)
Can I mix different brands of oils in Tohatsu gearbox?
It is strongly discouraged from mixing oils from different manufacturers or even different brands. The chemical composition of additives can react, leading to precipitation, foaming and loss of lubricating properties. If you move to another brand, you need to thoroughly wash the reducer.
How much oil is required for the Tohatsu 9.8 gearbox?
Volume of oil in the motor gearbox Tohatsu 9.8 It is approximately 0.35 to 0.4 liters (depending on the modification and year of production), and the exact volume is determined not by the liters, but by the level: the oil is poured until it flows from the upper hole.
What to do if the oil is constantly leaving the gearbox?
If the level is constantly falling, it means that the leakage is broken, the main reasons are: wear of the osteoils of the paddle shaft, damage to the osteoarthritis rings of the corks or a crack in the body of the lower unit, you need to make a defect and replace the osteoils.
Is TAD-17 oil suitable for outboard motor?
TAD-17 oil (or its modern analogues TM-5-18) formally corresponds to the class. API GL-5It is designed for heavy trucks and contains sulfur additives that can be aggressive against non-ferrous metals (bronze sleeves), often used in boat gearboxes. Outboard Gear Oil.