outboard motor Tohatsu 9.8 It is one of the most popular outboard motors among fishermen and small boat owners, depending on the quality of service, and the key is the proper care of the gearbox (or "foot," as it is often called), many owners face problems due to the banal ignorance of what oil to use, how often to change it and what errors in replacing lead to breakdowns.
In this article, we will look at all the nuances, from the choice of oil to the step-by-step instructions for replacing. You can not save on lubrication for the reducerWe're going to talk about how to check the oil level without any tools, and what to do if you start to have a foot noise after you've replaced it, and we're going to talk about the myths about the "perpetual" oils and tell you which brands are really trustworthy.
Why the oil in the leg Tohatsu 9.8 Is that important?
The boat gearbox works in extreme conditions: constant water exposure, high loads, temperature changes. The oil here performs three critical functions:
- 🛡️ Corrosion protection - prevents rusting of gears and bearings due to moisture.
- ⚙️ Lubrication of rubbing parts - reduces wear of gear teeth and increases the resource of the gearbox.
- 🔥 Heat removal - cools the mechanisms at long loads (for example, when trolling).
If the oil is old or poor quality, the consequences can be fatal:
⚠️ Attention: When working on dry or contaminated oil gear gear gear reducer Tohatsu 9.8 They wear out 5 to 7 times faster, and the first sign of a problem is the metal grinding of the gear shift and the back of the propeller, and if you ignore these symptoms, it costs 30 to 50 percent of the cost of a new engine to repair.
It is especially dangerous to use car transmission oils, because their additive package is not designed to work in an aquatic environment. GL-5 80W-90 It can lead to corrosion of the bronze parts of the gearbox after 50 hours.
what oil to use in the reducer Tohatsu 9.8?
Manufacturer Tohatsu Recommends the use of only specialized oils for boat gearboxes with markings API GL-5 and viscosity SAE 80W-90 or SAE 90But not all oils with this specification are equally good.
| Brand | Name of butter | Viscosity | Features | Approximate price (1L) |
|---|---|---|---|---|
| Tohatsu | Gear Oil | 80W-90 | Original oil, the optimal composition of additives for bronze gears | 1 200–1 500 ₽ |
| Quicksilver | Premium Gear Lube | 90 | Improved water protection, recommended for salt water | 1 400–1 600 ₽ |
| Yamalube | Gear Oil | 80W-90 | Good compatibility with motors Toatsu, affordable | 900–1 100 ₽ |
| Mercury | High Performance Gear Lube | 90 | High thermal stability, suitable for severe conditions | 1 300–1 500 ₽ |
Important: Oils labeled "LS" (Low Sulfur) are not suitable for Tohatsu 9.8 They do not contain enough sulfur to protect the bronze parts of the gearbox.
If you operate the motor in salt water, choose oils marked Saltwater or MarineThey contain additional anti-corrosion additives, and for fresh water, universal options will be suitable.
When and how often should I change the oil in my leg?
Manufacturer Tohatsu indicates in the manual the interval of oil change in the gearbox - every 100 hours or once a seasonBut this timeline is only relevant for ideal conditions, and in reality, the replacement rate needs to be adjusted.
- 🌊 Salt water Every 50-70 hours (salt accelerates the oxidation of oil).
- 🏞️ Contaminated water bodies (sand, sludge) - every 60-80 hours.
- ❄️ Extreme temperatures (below -10°C or above +30°C) - reduce the interval by 20-30%.
- 🔄 Frequent launches/stops (for example, when trolling) - oil ages faster due to condensation.
How to know if the oil is time to change casually?
⚠️ Attention: If you see metal shavings, water (emulsion) or blackened after you drain the oil, that's a signal that the gearbox is malfunctioning, and then it's not enough to just change the oil, you have to take your leg apart and check the gears.
You can check the condition of the oil visually:
Muddy color or presence of water (emulsion)
Metallic shavings or black particles
Smell of burns
Thick consistency (does not flow freely)
Oil levels below the minimum level--
Step-by-step instructions for replacing oil in the leg Tohatsu 9.8
For oil replacement you will need:
- 🔧 10 or 12 mm key (depending on the model).
- 🛢️ Capacity for draining the working (minimum 0.5 liters).
- 🧴 New oil (0.3–0.4 l for Tohatsu 9.8).
- 🧻 Gloves and rags.
- 🔨 Screwdriver (for some models, you need to remove the protective cap).
Step 1: Preparation of the engine
Set the motor vertically (e.g., on a stand or fasten it to the transom of a boat) Start the engine for 2-3 minutes so that the oil in the gearbox warms up, so it will merge faster and fuller. Then turn off the engine.
Step 2. Plum the old oil
Find the drain plug on the engine leg (usually at the bottom of the gearbox, closer to the screw). Place the container and unscrew the plug with the key. Let the oil drain completely (5-10 minutes). If the oil does not flow, check if the hole is filled with dirt.
What to do if the oil does not drain?
If the oil does not leak after unscrewing the plug, the reasons may be as follows:
1. The thickened butter Try to warm the gearbox with a hair dryer (maximum 60°C) or leave the engine in the sun for 1-2 hours.
2. The drain hole is clogged. Clean it with wire or compressed air.
3. The traffic is not fully unscrewed. - on some models Tohatsu The drain plug has double threading, check this in the manual.
4. Oil leak earlier If the gearbox is empty, this is a sign of malfunctioning of the glands or a crack in the body.
Step 3: Washing the gearbox (optional)
If the old oil was dirty or with metal chips, it is recommended to wash the gearbox.
- Turn the drain plug.
- Pour 100-150 ml of fresh oil through the upper hole.
- Scroll the screw manually (or briefly start the motor on idles) so that the oil is distributed.
- Pour the washing oil and assess its condition.
Step 4: Pouring new oil
Use only the original plug with the O-ring (if worn out, replace it). Pour the oil through the top hole until it starts to flow back out. Tohatsu 9.8 usually 300–350 mlTurn the plug with a force of 15-20 Nm (do not pull!).
After changing the oil, manually scroll the screw 10-15 times so that the oil is evenly distributed across the gears. Then check the level - add if necessary.
Common mistakes when replacing oil
Even experienced boat owners sometimes make mistakes that reduce the life of the gearbox.
- 🔧 Use of the wrong oil Automotive transmission oils (e.g.,
Castrol 80W-90) do not have the necessary additives to protect against water. - 🕳️ Short or overflowing oil - low level leads to oil starvation, high - to extrusion of the osteoils.
- 🔩 Swirling of stoppers without sealing rings - leads to leakage and water intake.
- 🌡️ Replace oil on a cold engine The viscous oil does not completely merge, the residues are mixed with the new.
- 🧹 Ignoring washing when changing the type of oil For example, when switching from mineral to synthetic.
Critical error: Using a sealant on the cork threads, which can lead to the oil getting sealant particles and jamming the gearbox.
Another common problem. tug-inMaximum tightening moment for drain and filler stoppers Tohatsu 9.8 — 20 Nm.Exceeding this value can lead to a failure of the thread or deformation of the gearbox body.
How to check the level of oil without special tools?
If you don’t have a probe or measuring cup, the oil level in the gearbox Tohatsu 9.8 You can check the "grandfather" way:
- Install the motor strictly vertically (use the level or check the plumb).
- Then, turn the top of the sleeve.
- Insert a clean wire or plastic tube with a diameter of 2-3 mm to the end.
- Take the wire out and measure the length of the wet area. 15–20 mm from the bottom of the gearbox.
If the level is below 10 mm, add the oil. If it is above 25 mm, drain the excess through the drain plug.
Check the oil level in the gearbox. Tohatsu 9.8 Every 20-30 hours, it takes 2 minutes, but it prevents expensive repairs.
What to do if there is a noise after the oil change?
If after changing the oil in the gearbox there was an extraneous noise (screaming, hum, knocking), the reasons may be as follows:
| A symptom. | Possible cause | Decision |
|---|---|---|
| metallic grinding | Insufficient oil levels or air intake | Add the oil, check the tightness of the plugs |
| idle hum | Wear of bearings or gears | Disassembly of the gearbox and diagnosis |
| Knocking on gear shifts | Water entering the oil (emulsion) | Complete oil replacement with washing |
| High-speed vibration | Poor quality oil or its overflow | Pour the excess or replace the oil with the recommended |
If the noise does not disappear after the oil is changed again, Don't delay the diagnosis.Wear of gear gears of gear gear gears Tohatsu 9.8 progresses very quickly - for 1-2 outlets on the water, a small problem can grow into the need to replace the entire gearbox (cost - from 20,000 ).
FAQ: Frequent questions about oil in the leg Tohatsu 9.8
Can I mix different brands of oil?
Mixing oils from different manufacturers not recommendedEven if they have the same size (80W-90Other additive packages can react, resulting in sedimentation or loss of properties. If you need to add oil, use the same brand or complete replacement.
How much oil is needed to replace the entire Tohatsu 9.8?
Volume of oil in the gearbox Tohatsu 9.8 — 300–350 ml. Buy litre packaging to have enough to replace with stock (for example, for washing or topping). original oil Tohatsu Gear Oil It is sold in 1 liter bottles.
What happens if you don’t change the oil in your leg?
The consequences depend on the mileage, but the typical scenario is:
- 🔹 100-200 motor-hours - increased wear of gears, the appearance of metal shavings.
- 🔹 200-300 hours of motor-training - backlash, noise when changing gears.
- 🔹 300+ motor-hours - jamming the gearbox or breaking the gear teeth (repair will cost 15,000-30,000 ).
In salt water, the process is accelerated by 1.5-2 times.
Can synthetic oil be used?
Yeah, synthetic oil. 80W-90 API GL-5 fit Tohatsu 9.8, but with reservations:
- ✅ Pluses: better fluidity at low temperatures, retains properties longer.
- ❌ Cons: High price, not all brands are certified for outboard motors.
When switching from mineral to synthetic oil, be sure to rinse the gearbox.
How often do I check the oil in the gearbox?
Check the level and condition of the oil:
- 🔹 Before the first watering of the season.
- 🔹 Every 20-30 hours (or after long trips).
- 🔹 After blows of the screw on the obstacle (risk of damage to the glands).
- 🔹 If the motor has been standing idle for a long time (condensation in the gearbox is possible).
The inspection takes 2-3 minutes, but saves thousands of rubles on repairs.