outboard motor operation Tohatsu 18 Not only does it require fuel control, but it also requires regular maintenance of the bottom of the unit. The water flow in which the screw operates is aggressive to metal, and the only protection against corrosion and bullies is a quality lubricant. Many owners wonder what kind of oil to use in the Tohatsu 18 gearbox so as not to damage the mechanism and prolong the life of the unit.
Incorrect choice of lubricating fluid or violation of replacement intervals can lead to emulsification, loss of lubricating properties and, as a result, expensive repairs. transmissionIn this article, we will discuss in detail the manufacturer's technical requirements, permissible analogues and step-by-step algorithm of actions during replacement.
And you have to consider that the gearbox is operating in extreme conditions of temperature extremes and constant contact with water, which is why the viscosity and adhesive properties of the fluid are critical, and ignoring these parameters often causes the coils or gears of the main gear to fail.
Manufacturer requirements and oil specifications
Japanese concern Tohatsu It sets strict standards for the lubricants used in its products. For an 18 hp model, as for most two-stroke and four-stroke engines in its lineup, the use of specialized transmission fluids is critical. API GL-4 or GL-5.
Automotive oils for manual transmissions of passenger cars are only permitted if the chemical composition is fully in line with marine requirements, with additives that prevent foaming and oxidation in contact with water being a key difference.
⚠️ Note: It is strictly forbidden to use engine oils (API categories SJ, SL and above) in the gearbox, as they do not have the necessary viscosity and can lead to extrusion of the osteoils.
Viscosity is also important, and for temperate climates and standard operating conditions, a liquid with an index is considered the best choice. #90 This provides a stable oil film at operating temperatures of the unit.
If you frequently operate a boat at very low temperatures, consider synthetic oil options that keep fluidity in the cold, but only if it is allowed by the manual for your motor series.
Volume and frequency of replacement
Regular maintenance of the lower part of the motor directly affects its durability. Tohatsu M18The primary oil change must be made after running in, usually 10 hours, to remove the metal shavings formed by grinding gears.
The procedure is repeated annually or every 100 hours, whichever comes first. However, when you are in heavy use or frequent salt water, it is recommended to shorten the intervals.
As for the quantity, the volume of the crankcase of the 18 hp model is approximately 330-350 mlThe exact value may vary slightly depending on the year of release and modification of the lower unit, so always focus on the level of oil in the viewing window or control hole.
You don't need to put the lubricant on the eye. Lack of volume will lead to the gears working in oil starvation mode, and excess will create excessive pressure when heated, which can damage the seals.
Step-by-step instructions for oil replacement
The process of replacing the transmission fluid in the engine Tohatsu 18 It's technically simple, but it requires a sequence of actions, and a breakdown in technology can cause the gearbox to suffocate or fill the crankcase incompletely.
First, you need to put the outboard motor upright, so you'll get the right fluid level, and you'll drain the waste, and then you'll have to prepare the waste oil tank and the plug-unwinding tool.
☑️ Preparation for oil replacement
First, the bottom drain plug is unscrewed, the bulk of the workout drains through it, and then the top control hole (or probe hole, depending on the design of the lower unit) is unscrewed, which is necessary to ensure ventilation and faster drainage.
After the liquid has drained completely (usually 10-15 minutes), the magnets must be inspected on the corks. The presence of fine metal dust ("silver") is normal, but large fragments of metal or shavings indicate a serious malfunction.
Sequence of action:1. Unscrew the bottom plug.
2 Unscrew the top cork.
3. Pour the butter.
4. wash the reducer (if necessary).
5. Inject new oil from below before appearing in the upper opening.
6. To tighten the top cork.
7. Quickly remove the syringe nose and twist the bottom plug.
The fill is made entirely from the bottom up with a special syringe or a long spout of oil, which allows you to force the air out of the crankcase, and as soon as fresh oil leaks out of the upper hole without bubbles, the top stopper is closed.
Diagnosis of the state of the reducer by oil
The color and consistency of the drained liquid can tell you a lot about your health. transmission-assemblyA careful inspection of the workout helps to identify problems at an early stage, preventing major repairs.
In normal condition, the oil should be transparent, amber or light brown, slight darkening due to the natural aging of additives and saturation with metal microparticles during the break-in period is allowed.
⚠️ Warning: If the butter has become "coffee with milk" or has become cloudy white, this is an unambiguous sign of water entering the gearbox.
The presence of large metal particles, scales or a clear smell of burns in the oil indicates the destruction of bearings or gears, in which case a simple change of oil will not help - defective and repairing the mechanism is required.
Why does the emulsion appear?
Emulsion (water in oil) is most often formed due to wear of the screw coil or the oal of the switching rod, and it can also be caused by a microcrack in the body of the lower unit or a weakening of the puff of the plugs. Water condenses inside when the motor cools after operation, creating a vacuum that sucks water through leaky seals.
Regular visual inspection allows you to replace penny oils in time and avoid replacing the entire node. Ignoring the change in color of the lubricant is the right way to jam the gearbox.
Compatibility table and recommended products
There are many lubricants on the market, but not all of them are suitable for water engineering. Below is a table with recommended products and their analogues, which have proven themselves in the operation of motors. Tohatsu.
| Type of product | original | Analogues | Features |
|---|---|---|---|
| Original | Tohatsu Gear Oil #90 | — | Perfect compliance with specifications |
| Mineral | Motul Gear 300 | Liqui Moly Marine Gear Oil | High thermal stability |
| Synthetics | Castrol Syntrans | Mobil Delvac Synthetic | Working in extreme temperatures |
| Budgetary | TNC Trans Gear | Lukoil TM-5 | Requires more frequent replacement |
When choosing an analogue, it is important to pay attention to the marking GL-5GL-4 class oils may not contain sufficient anti-shooting additives for hypoid gears, which are often used in outboard motor gearboxes.
Using cheap industrial oils without marine tolerances is not a savings, their resource is much smaller, and the risk of corrosion of internal surfaces is much higher.
Original Tohatsu oil is the safest choice, but quality branded Marine or GL-5 oils are also completely acceptable.
Frequent errors in service
Even experienced boat owners sometimes make mistakes that can cost the engine a lot of service, and one of the most common is trying to pour oil on top of the boat through a sapoon without using a syringe, which causes traffic jams in the air, and the gearbox runs dry, despite being formally full.
Another mistake is reusing old plugs or damaged O-rings, aluminum washers or rubber rings are designed for single use, and twisting them makes them leaky.
Excessive force in tightening the plugs is also dangerous. The aluminum of the gearbox body is soft, and it's very easy to break the thread. You need to twist the plugs with moderate force, relying on the force of the hand or a dynamometer key with a small limit.
⚠️ Warning: Never start the engine with the drain holes open or without the oil in the gearbox, even for a few seconds.
Owners also often forget to check the oil level after a long parking period, if the engine stood on its side or upside down for a long time, the oil could leak into the lower unit or, conversely, leak through the glands, and check the level before the first start of the season is mandatory.
Can I mix different manufacturers in a gearbox?
Mixing oils of different brands and bases (mineral with synthetics) is highly discouraged. Chemical reactions between additive packets can lead to precipitation, foaming or loss of lubricating properties. If you don't know what was poured before, it's best to wash the gearbox with a small amount of new oil before the final pouring.
What to do if water gets into the oil?
You have to drain the emulsion completely, wash the gearbox with a solar or a special wash oil, then blow it with compressed air, and then replace the screw and rod coils, because that's where most water is sucked, and then you can pour fresh lubricant after the cause of the leak is eliminated.
How often should I change the pads under the traffic jams?
Ideally, with every change of oil, aluminum washers and rubber rings lose their elasticity and deform, no longer sealing the connection, and using old pads is a lottery, where the gain is the lack of water in the gearbox, but the risk is too great.
Do I need to warm up the gearbox before draining the oil?
Warm oil is less viscosity and drains more easily, carrying more dirt and metal suspension, and just let the engine work for 5-10 minutes before the replacement procedure.