Owners of outboard motors often confuse the lubricant for the fuel mixture and the liquid circulating in the bottom of the unit. Reductor oil It has the critical function of protecting the gears and bearings of the propeller from wear, corrosion and overheating, and unlike gasoline oil, it doesn't burn, but rather works in a closed loop, creating a protective film on the rubbing parts.
The wrong choice of lubricant can cause expensive nodes to fail quickly, and the water that enters the osteoils mixes with the lubricant, forming an emulsion that loses its properties. what oil to use in the gearbox 2 stroke outboard motorIt is a basic skill for any boater who wants to extend the life of his iron horse.
In this article, we will look at the specifications of suitable liquids, look at the viscosity table and learn how to diagnose problems by the appearance of the working out, you will learn why you can not use conventional car transmissions and what additives are really necessary for sea or fresh water.
Lubricants Requirements for lower unit
The bottom of the outboard motor, or lower unit, is extremely extreme, and the constant contact with water, extreme temperature changes and high mechanical loads require specialized compounds. hydrophobicity (water repellent) and resistance to emulsification.
If the ordinary oil when water is ingested turns into “mayonnaise” or emulsion, then a specialized oil for the use of the oil is used. gear case This allows the water to settle down at the bottom of the crankcase, where it can be drained, keeping the top layer of lubricant for the workers, and using the wrong materials leads to corrosion of the gears and jamming of the gearshift mechanism.
⚠️ Warning: Never use engine oil for internal combustion engines (even synthetics) in a gearbox, which lacks the necessary metal adhesion and quickly loses its viscosity under the load of gears.
Modern outboard gearbox oils often contain EPs, which are activated under high pressure at the point of contact of the gear teeth, preventing metal from grasping, especially for high-powered motors that are loaded on the gear teeth. mainline It's huge.
Types of oils: mineral, semisynthetics and synthetics
The choice of the base oil base directly affects the intervals of replacement and protection of the units. There are three main types of liquids on the market, each of which has its own application specifications depending on the operating conditions and type of motor.
Mineral oils They're made from refined oil. They're good lubricants and they're inexpensive. But at low temperatures, they thicken very thickly, which increases the drag when you scrolle the screw, and at high temperatures, they can oxidize faster than synthetic ones, and they're useful in medium-powered motors and seasonal heat-climate operation.
Synthetic oils They're artificially created, they have a stable molecular structure, they keep fluidity in the cold, they don't lose their viscosity when they're heated, they get better at removing heat from gears and they resist aging longer, and for high-speed boats and highly forcing motors, that's the only sure choice.
Semi-synthetic formulations are a compromise, combining the price of mineral water and some of the properties of synthetics. GL-4 or GL-5Hypoid gears, which are often used in gearboxes of outboard motors (where the gear axles intersect), require a class of gear. GL-5 It's high in anti-sharp additives.
Table of viscosity and specification of oils
Viscosity is a key parameter that determines how easily oil will be pumped and create a protective layer. For outboard motors, oils with a SAE 80W-90 or 90 viscosity are most often used. In cold regions, more liquid variants such as 75W-90 are allowed.
Below is a table that helps determine the optimal viscosity depending on the temperature conditions of your boat.
| Type of oil (SAE) | Temperature range (°C) | Recommended application | Features |
|---|---|---|---|
| 80W-90 | -20 to +35 | Universal, summer/interseason | Standard for most motors |
| 85W-140 | -10 to +45 | Hot climate, high loads | High viscosity, thickness |
| 75W-90 | -40 to +35 | Cold climate, winter storage | Easy start, low friction. |
| 90 (mono) | 0 to +40 | Warm season | Stable film under heating |
It is important to follow the specifications of the manufacturers. Most brands (Yamaha, Mercury, Tohatsu) recommend oils that meet the standard. NMMA FC-W or specification API GL-5The use of oils with molybdenum additives (often labeled as MoS2) in gearboxes with bronze washers or synchronizers may be prohibited, as the sulfur in additives causes corrosion of non-ferrous metals.
Always check the oil's compatibility with seal materials. Aggressive synthetics can cause old rubber cuffs to swell, leading to leakage.
When mixing oils from different manufacturers or bases, precipitation may fall out. If you do not know what was poured before, it is better to completely wash the gearbox before pouring the new composition.
How to check the condition of the oil in the gearbox
Regular diagnosis of lubrication status allows you to identify problems with the leakiness of the omentums at an early stage, it is recommended to check before each release to the water or once a season, to do this, you need to turn the lower and upper stoppers of the gearbox.
Healthy oil has a clear amber or dark brown color and a uniform consistency, and if you see the following signs when you leak out, it's a malfunction signal:
- 💧 Milk color: This is an emulsion, which means that water has been trapped in the gearbox. The ossuaries need to be replaced.
- 🌫️ Metal shavings: The presence of large metal particles on the magnet of the lower cork or in the oil stream indicates wear of gears or bearings.
- 🌫️ Smell of burn: Evidence of overheating of the nodes or the use of inappropriate oil.
A small amount of fine magnetic dust ("silver") on the cone of the bottom stopper is normal for a break-in motor, but if the chips are large, similar to flakes or scales, you need to open the gearbox for defects.
⚠️ Note: If the butter is "coffee with milk", the engine is prohibited. The water in the gearbox will corrosion the propeller bearings in a matter of hours of operation.
For a precise diagnosis, you can drop the oil on a white napkin, and if there is a clear halo around the spot and a dark spot in the center, the oil has oxidized and needs to be replaced, even if there is no water.
Step-by-step instructions for oil replacement
The procedure for replacing the lubricant in the gearbox of a two-stroke (and four-stroke) motor is almost identical and does not require a complex tool. The main rule is that the oil is always poured from the bottom up to displace air and avoid bubbles.
You'll need an oil syringe (manual or pneumatic), a working tank, a rag and a new oil to work with, and you'll need to put the outboard motor upright, which is critical for the right fluid level.
☑️ Replacement tools
First, unscrew the top plug (control), then the bottom plug (drain). Give the waste oil to drain completely into the prepared container. Pay attention to the color and presence of chips, as described in the previous section. After draining, it is recommended to wash the gearbox with a small amount of fresh oil or a special washing liquid if the previous one was severely contaminated.
Put the syringe nose in the bottom hole. Start slowly pumping new oil. Once the oil leaks out of the top hole, quickly twist the top plug without stopping the pressure of the syringe to create a little excess pressure. Then, as you continue to hold the syringe, twist the bottom plug.
Sequence of action:1. Unscrew the HIGHER COMPLETE.
2. Unscrew the bottom plug.
3. drain the workout.
4. pump new oil into the bottom hole.
5. When oil appears in the upper hole - twist the upper plug.
6. Crack the bottom of the traffic.
Principle: Filling is always done through the bottom hole to avoid air traffic jams that can lead to oil starvation of bearings.
Be sure to replace the sealing rings (gassings) on the corks. They are often bundled with oil or sold separately. Old flattened pads are a guarantee of future leakage.
Frequent errors in the maintenance of lower unit
Even experienced motorists sometimes make mistakes that reduce the life of the unit. oil-flowExcess heat pressure (thermal expansion) can squeeze out the glands, and oil will enter the water, polluting the environment, and water will enter the gearbox.
Another mistake is ignoring seasonality, and trying to save money and pour summer viscous oil in the winter will cause the thick mass to be delayed in cold start-ups, and the bearings will run dry for the first few minutes, causing the metal to micropaint.
- 🚫 Use of work-off: Never put the oil back in, even if it looks clean. It already contains wear and oxidation products.
- 🚫 Brand mixing: Chemical additive packages from different manufacturers can come into conflict.
- 🚫 Plunging traffic jams by the eye: An unwounded cork will fly out on the go, twisted - will break the thread in the aluminum case.
What happens if you mix up the traffic?
In some motors, the corks have different thread lengths or cone shapes, and if you screw a long cork into a short hole, it can rest on the gear and block the rotation of the screw, which will break the switching mechanism or cut the gear when you try to move.
It is also a mistake to change the oil only “by color”; even if the oil darkens but does not show signs of emulsion or shavings, it still needs to be changed according to the regulations (usually once a season or every 100 motor hours), since additives are produced over time.
FAQ: Frequently asked questions
Can I use car transmission oil in a outboard motor?
Technically, it can be done if it is in the class. API GL-5 However, car oils do not contain special additives to protect against corrosion in an aqueous environment and can be more quickly emulsified when moisture is ingested.
How often should you change the oil in the gearbox of a two-stroke engine?
The recommended interval is once a season (before or after winter storage) if the engine is in intensive operation (more than 100 hours a year), a replacement is carried out every 100 hours.
How much oil is needed for a medium motor gearbox?
Volume depends on the power and model of the motor. For motors with a capacity of 2-6 hp, it is usually required about 150-200 ml. For motors 8-15 hp - 300-350 ml. Powerful motors (30+ hp) can require from 400 to 600 ml.Owner's Manual) to a specific model.
Why did the oil in the gearbox turn white?
White means that the gearbox has water, and that's because of the wear of the propeller coil or the ossicle of the gear shifter, and you can't run a motor with that oil, you have to replace the oil and the oil.