Oil leakage from lower unit weep hole is one of the issues some outboard owners encounter.
When this issue occurs, oil is seen dripping out of the lower unit.
Some of the reasons why this occurs include worn out seals and gasket, use of wrong propeller size, damage of lower unit housing, loose or damaged drain plug and damaged propeller shaft.
Any of these problems can easily cause a leakage in the lower unit.
When the lower unit leaks, the oil that helps in lubricating the mechanical parts in the lower unit will be lost.
This can easily lead to the damage of these parts due to friction.
Apart from friction damaging these parts, water can enter and cause corossion.
That is why issues like oil leakage from the lower unit is very critical and should be corrected immediately they are spotted.
This will help extend the lifespan of the outboard motor and improve performance.
Why Is Oil Leaking From Lower Unit Weep Hole
1. Worn out seals
The seals in the lower unit are designed to prevent oil from leaking out of the unit. Over time, these seals will crack, wear ou or develop cracks.
These issues will cause oil to leak through the seal and out of the weep hole.
The seals are typically made of rubber or another flexible material that can sustain damage over time due to exposure to heat, pressure and friction as the outboard motor keep functiining.
When the seals become worn out, they will no longer be able to create a tight seal around the moving parts of the lower unit.
This will easily allow oil to escape.
This can be very dangerous because the oil in the lower unit is essential for lubricating the gears and preventing wear and tear due to excess friction on the moving parts.
When oil leaks out of the lower unit, the gears can become damaged which can lead to more serious problems with the engine.
If you notice oil leaking from the lower unit weep hole, it is important to have the seals inspected and replaced where necessary.
This will help prevent further extended damage to the engine thereby ensuring safe operation on the water when boating.
2. Damaged propeller shaft
A damaged outboard motor propeller shaft can cause oil leakage from the lower unit in some ways:
The first way a damaged propeller shaft can cause oil leakage from the lower unit is by causing damage to the seals in the lower unit. The propeller shaft runs through the lower unit of the outboard motor.
If it is bent or damaged, it can put pressure on the seals.
This will cause the seals to become damaged or fail.
This can allow oil to escape through the weep hole and lead to extended damage to the lower unit and engine parts.
Another way a damaged propeller shaft can cause oil leakage from the lower unit is by creating excessive vibration in the lower unit.
A faulty propeller shaft can cause the propeller to spin unevenly.
This will end up creating vibrations that can damage the seals in the lower unit.
This can cause the seals to easily become damaged thereby allowing oil to leak out through the weep hole.
3. Loose or damaged drain plug
The drain plug is an essential component in the lower unit of an outboard motor.
It is designed to allow the oil in the lower unit to be drained for maintenance purposes.
After maintenance is over, the drain plug has to be sealed to prevent oil from leaking out of the unit.
If the drain plug is not tightly secured, it can cause oil to leak out of the lower unit.
A loose drain plug can allow oil to escape through the threads of the plug which can cause a slow leak that may not be immediately noticeable.
If not corrected early and fast, this can lead to a loss of oil in a higher volume which will cause damage to the engine components.
4. Overfilled gear lube
When oil leaks from lower unit weep hole, it can be due to excess oil in the lower unit.
The excess gear lube can create increased pressure within the lower unit.
This pressure buildup can cause seals and gaskets to become faulty thereby leading to oil leakage.
Overfilled gear lube can also lead to foaming. This foaming can create air pockets that will prevent the gear lube from properly lubricating the gears and bearings.
Without proper lubrication, these components can experience increased wear and tear which will cause the seals and gaskets to fail which will lead to oil leakage.
5. Water in gear lube
Another reason why oil leakage from lower unit weep hole occurs is when there is water in gear lube.
Water can cause rust and corrosion on metal surfaces inside the lower unit such as gears, bearings and shafts.
This can lead to wear and tear which can cause seals and gaskets in the lower unit to fail and cause oil to leak out.
Apart from corrossion, water can mix with the gear lube and cause it to emulsify or form a creamy white substance.
This emulsified gear lube can become less effective in lubricating the gears and bearings in the lower unit thereby leading to increased wear and tear and with leakage of oil from the lower unit.
When the temperature is low, water in the gear lube can freeze and expand thereby causing damage to the seals and gaskets in the lower unit.
This can lead to oil leakage when the outboard motor is in use.
6. Damaged lower unit housing
The lower unit housing is the protective casing that surrounds the lower unit of an outboard motor.
This housing is designed to prevent water from entering the lower unit.
It is also designed to keep lubricating oil inside the unit without leakage.
But if the lower unit housing is damaged, it can cause leakage of oil from the lower unit.
When the lower unit housing is damaged, it creates openings or cracks that allow water to move into the lower unit.
Water can mix with the oil inside the lower unit.
This will dilute the oil in the lower unit and reduce its lubricating properties.
This can cause excessive wear and tear in the lower unit components.
7. Improperly installed seals
Improperly installed seals in the lower unit can cause oil leakage by allowing oil to escape from the openings.
Seals are an important component of the lower unit as they prevent oil from leaking and water from entering the unit.
If the seals are not installed properly, they can become damaged, worn or misaligned which can lead to oil leakage.
When the seals are not installed properly, they can fail to create a proper seal between the lower unit and upper driveshaft housing.
This can easily allow oil to leak out of the lower unit and cause damage to the lower unit components.
Water can enter the lower unit and mix with the oil thereby causing the oil to lose its lubricating power.
A wrong installation of seals can also cause the seal to wear out quickly.
This will easily lead to oil leakage.
This can happen if the seal is not aligned correctly which will lead to excess friction between the seal and the rotating shaft.
Over time, this can cause the seal to wear out and create an opening which will cause water to enter or oil to leak from the lower unit.
8. Improperly installed drain plug
An improperly installed drain plug can cause oil leakage in the lower unit.
The drain plug is a small component that is located at the bottom of the lower unit.
It is used to drain oil from the lower unit during maintenance.
If the drain plug is not installed properly, it can cause oil to leak from the lower unit.
This can happen if the drain plug is not tightened secured or if it is cross-threaded during installation.
When the drain plug is not tightly secured, oil can leak out of the lower unit.
This will lead to reduced lubrication and damage of the lower unit parts.
9. Improperly installed gaskets
An improperly installed gasket can cause oil leakage to occur in the lower unit.
The gasket is a thin and flexible material that is placed between two surfaces to create a seal. In the lower unit, the gasket is used between the lower unit and the upper driveshaft housing to prevent oil from leaking out of the lower unit.
If the gasket is not properly installed, it can cause oil to leak from the lower unit.
This can happen if the gasket is misaligned during installation, worn out or if it is not properly tightened.
When the gasket is misaligned during installation, it can create gaps between the lower unit and upper driveshaft housing.
This will cause oil to leak out of the unit and potentially damage the lower unit components. If the gasket is not tightened well, it can also cause oil to leak from the lower unit.
When the gasket is not compressed enough between the two surfaces, it will not be able to create a tight seal thereby allowing oil to escape through leakage from the lower unit.
10. High-speed operation
When a boat moves at high speeds, the lower unit of the engine generates heat due to friction from the movement of the gears and other mechanical components.
This heat causes the oil in the lower unit to expand.
This leads to an increase in the pressure inside it.
If the pressure inside the lower unit is too high, it can force oil out of the weep hole which is designed to release excess oil and prevent damage to the seals and bearings inside the engine.
Additionally, high speed can cause the lower unit to vibrate which can also contribute to oil leakage.
This vibration can cause the seals and gaskets inside the engine to wear out and become damaged thereby allowing oil to leak from the weep hole.
11. Age of the boat
The age of the boat can cause oil leakage from the lower unit weep hole in several ways.
Over time, the seals and gaskets that prevent oil from escaping from the lower unit can wear out and become brittle.
This will cause small cracks and gaps to form. Due to these cracks, oil will leak out of the weep hole.
As the boat ages, its engine and lower unit components will become worn and damaged which can also increase the probability of oil leakage.
If the boat is not properly maintained, oil leakage from the lower unit weep hole can easily occur.
12. Poor maintenance
Poor maintenance can cause oil leakage from the lower unit weep hole in several ways. Some of the most common causes are:
a) Worn or damaged seals: The seals inside the lower unit that prevent oil from leaking out can wear out over time especially if they are not properly maintained.
If the seals are worn or damaged, they can fail to keep the oil inside the lower unit.
This will cause the oil to leak out through the weep hole.
b) Overfilling: oil leaking from lower unit weep hole can occur if oil is overfilled in the lower unit.
If the lower unit is overfilled with oil, it can cause excess pressure inside the unit which can force the oil out through the weep hole.
This can happen if the oil level is not checked regularly and topped up as needed.
c) Contamination: If dirt, debris, or other contaminants get into the lower unit, they can cause damage to the seals and other components which can lead to oil leakage.
This can happen if the lower unit is not properly cleaned and maintained.
d) Corrosion: If the lower unit is exposed to saltwater or other corrosive materials it can cause corrosion to the seals and other components in the lower unit which can lead to oil leakage.
This can happen if the lower unit is not properly rinsed and maintained after use in saltwater.
13. Impact damage
When the lower unit of an outboard motor is subjected to impact from rocks or other objects underwater, the housing may sustain damage. Such damage can result in cracks or fractures in the lower unit housing.
When this occurs, the seals within the lower unit can also be damaged thereby leading to oil leakage.
The weep hole is designed to allow water to drain out of the lower unit but when there is a crack or fracture in the housing, oil can also leak out through the weep hole.
This can cause a loss of lubrication and severely damage the internal components of the lower unit.
14. Improperly sized propeller
An improperly sized propeller can cause oil leakage from the lower unit weep hole because of the increased load on the engine.
When the propeller is too large or too small, it can cause excessive strain on the engine which in turn can cause the gears in the lower unit to wear down more quickly.
An oversized propeller can cause some misalignment of the driveshaft which will easily destroy the gasket and seals thereby leading to leakage of oil from the lower unit weep hole.
How To Prevent Oil Leakage From Lower Unit Weep Hole
1) Store Outboard Motor Well
When the outboard motor is not in use, it has to be properly stored.
This is because some of the damages that occurs in the lower unit of an outboard motor is due to bad storage.
When an outboard motor is not stored well, it can come in contact with severe impact with hard objects.
This will end up damaging the lower unit casing.
Due to this, casualties like leakage of oil from the lower unit might occur.
To prevent this, the outboard motor has to be well stored when not in use.
2) Prompt Maintenance Of Outboard Motor
Prompt maintenance can prevent the leakage of oil from the lower unit weep hole by identifying and addressing potential issues before they become major problems.
Regular inspections can help detect any signs of wear and tear such as cracks, dents or corrosion that could lead to leaks.
Changing the oil regularly can help keep the seals and gaskets in good condition thereby reducing the risk of oil leakage from the lower unit of the outboard motir.
Using high-quality lubricants and following the manufacturer’s recommendations for maintenance can help ensure that the lower unit remains in good working order and minimize the risk of oil leaks.
3) When changing oil, ensure that the drain plug is tightened properly
Another way to prevent leakage of oil from the lower unit weep hole is to ensure that the drain plug is tightly fitted.
The drain plug is a threaded bolt that is screwed into the bottom of the lower unit casing to help drain oil from the lower unit.
When the drain plug is not tightly secured or becomes loose due to wear and tear, it can cause oil to leak from the weep hole which is located above the plug.
Tightening the drain plug with the appropriate torque can create a secure seal between the plug and the lower unit casing thereby preventing oil from escaping through the weep hole.
It is essential to follow the manufacturer’s recommended torque specifications while tightening the drain plug to avoid over tightening or under tightening.
This is because over tightening and under tightening can lead to oil leakage.
4) Use the correct propeller Size
Always make use of the right and compatible propeller size.
If the propeller is too small, it can cause excessive slippage which can lead to overheating and damage to the lower unit components.
This can result in oil leakage from the weep hole.
On the other hand, if the propeller is too large, it can cause excessive strain on the engine which can also lead to damage and oil leakage. That is why it is very important to choose the correct size of propeller for your outboard motor to ensure proper performance and prevent oil leakage from the lower unit weep hole.
5) Replace Worn Out Seals And Gaskets
Replacing worn out seals and gaskets in the lower unit of an outboard motor helps prevent the leakage of oil from the weep hole.
If there is any leakage of oil from the lower unit, it can mix with the water and cause damage to the engine.
By replacing worn out seals and gaskets, the oil is prevented from leaking out of the lower unit and into the weep hole.
This helps ensure that the engine is properly lubricated and protected from damage caused by oil leakage.
6) Avoid Extremely Rocky And Shallow Water Bodies
If the lower unit is scraped or damaged by rocks or shallow water, it can cause the seals to fail and oil to leak out of the weep hole.
To prevent this, it is essential to avoid rocky and shallow water whenever possible.
When boating in areas with potential hazards, it is important to proceed slowly and carefully while keeping an eye on the depth finder and scanning the water ahead for any obstacles.
This is one of the ways in which you can prevent leakage of oil from the lower unit weep hole.