Choosing and replacing transmission oil in a boat engine

Transmission oil for boat engines is used exclusively to protect the gear parts. High-quality lubricant has increased anti-corrosion properties and contains a complex of additives that prevent the wear of gears when the mechanism works in difficult conditions.

Transmission oil for boat engines


The nature of oils operating in the mechanisms of car transmission is influenced by three fundamental factors:

  • The speed of rotating gears
  • Temperature;
  • the amount of pressure at the points of touch of the jagged pair.

Temperatures in boat gearboxes can vary within fairly free limits, from environmental temperature to gears (200-250 degrees Celsius).

Transmission oil in boat engine gearbox

These parameters are more related to the size of the mechanical impacts and the speed at which the gears are shifted. As the engine revs increase, the thickness of the oil film decreases, which increases the risk of increased wear and tear of the teeth.

Unlike machine transmission, the boat engine gearbox works in more difficult conditions. The engine of the boat is constantly in the aquatic environment, and the speed of the current and the density of the liquid (fresh, salty) are added to the factors already listed.

Therefore, the lubricant for boat engines must also meet some special requirements:

  • To protect rubbing parts in high humidity conditions (water, etc.)
  • Have high anti-corrosion rates;
  • have enough viscosity to work in extreme conditions.

Transmission lubricant consists of the basis and complex of chemical additives that affect the performance of oils. Depending on the technical characteristics of the boat engine, an appropriate set of modifiers is selected.

Types of additives

Lubricants for PLM should provide the utmost protection of reducer parts from moisture, even when sealing elements are worn out. Special modifying additives protect oil from mixing with water (emulsion formation) and provide a stable film on the surface of the gears:

Additives in transmission oil of boat engines

Anti-foam additives are silicon organic substances that prevent the formation of foaming substances.

Anti-friction fluoride-containing compounds reduce friction by 40%, prevent the formation of microfractures, chipping, and give metal surfaces hydrophobe properties.

Antioxidative additives contain phosphorous and sulphurous compounds. They prevent the oxidation of oil, which can leak inside the gearbox when the latter is operated in extreme conditions, as well as by direct contact with seawater.

Anti-bullying and anti-wear additive segregated are chemical reagents that seal oil coatings in the places of contact of rubbing elements (polymers, sulfides, etc.). At the point of touching the gears formed a thin strong coating of iron sulfide, which when the temperature increases melts and prevents bullying, snout and wear.

Anti-corrosion additives. They are especially useful for boat engines operating in seawater.

Classification of transmission oils for boat engines

The first type of oils is mineral. They have an affordable price and are suitable for all domestic models. The basis of these liquids are residual products of direct oil distillation. Then the modifying additives are added to this mixture and a high-quality oil emulsion for boat motors is produced.

What a transmission oil for boat engines

The next type is synthetics obtained through the synthesis of hydrocarbon compounds with the addition of improving components. The oil has a stable viscosity, the index of which does not change over the life of the life.

The third variety of lubricants is semisynthetics, which is a mixture of mineral and synthetic base (30:70%). Such brands are inexpensive, and the quality is almost as good as synthetic.

Replacing oil with your own hands

For each type of boat engine, the manufacturer recommends a certain class of transmission oil. If the unit's passport does not include a lubricant brand, there are universal materials — SAE 80W-90 and SAE 85W-90.

Replacing transmission oil in a boat engine

The sequence of work:

  1. We hang the unit vertically, at some distance from the ground. To do this, we use a special stand or stand.
  2. Under the drain hole set the container.
  3. Remove the stub of oil control.
  4. Turn out the cork of the bay hole.
  5. Unscrew the drain bolt and wait for the emulsion to completely flow out of the gearbox. Then we change the pad on the cork and close the hole.
  6. Fill fresh oil until it appears at the exit of the control window.
  7. Set the bay bolt in place.

Wipe the rag swiping body of the gearbox and wait a few minutes for all the liquid glass to the bottom of the carter. Through the viewing window or with the help of a probe check the level of oil. Insufficient lubricant can cause premature wear and engine failure.

Алексей Назаров/ автор статьи

Руководитель сети СТО с огромным стажем работы.

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