Water in boat engine oil what to do?

Engine oil plays an integral role in the proper functioning of a boat engine. The engine oil in a boat engine is also responsible for lubrication of the engine parts, prevention of corrosion, and cooling the boat engine to prevent overheating.

Did the boat engine oil get mixed with water, and you didn’t know how to separate them? A normal boat engine oil is light bronze or maple in color, but boat engine oil contaminated with water becomes milky in color.

This is a sign that something has gone wrong in your boat engine that needs to be addressed immediately to avoid severe damages.

Looking solution for water in boat engine oil? Alright! There are various methods for removing water from boat engine oil. You don’t necessarily need oil extractors to get rid of water in outboard motor oil.

In this article, we will discuss why water is in boat engine oil and how to get water out of boat engine oil.

Reasons for Water in Boat Engine Oil

1. Blown Head Gasket

Boat engine oil would get contaminated with water and appear milky when you have a damaged head gasket. A head gasket is a vital component of an engine that aids in sealing the combustion chamber in the engine.

The head gasket is located between the cylinder head and the engine block.

It prevents harmful gasses from exiting the chamber by directing them through the exhaust system.

When your head gasket in your boat engine gets blown up, the coolant leaks and mixes with the oil.

2. Condensation

Condensation occurs when gas has been converted into liquid. Water could get mixed with oil through condensation.

As the engine of your boat heats up and cools down, it can cause condensation. The condensed liquid gets into a boat’s engine and contaminates the engine oil, changing it from a maple color to a milky color.

3. Crack in the Engine Block

A crack in the engine block could cause water to get mixed up with the engine oil. When there’s a severe crack in the engine block, the antifreeze fluid can find its way through the crack and mixes with the engine oil.

Removing Water from Boat Engine Oil

Method 1: Replace Bad Head Gasket

A head gasket helps to prevent the engine oil and coolant from entering into the cylinders.

A head gasket is an integral component in an engine, and when it gets damaged, it can cause defaults, one of which is the appearance of milky engine oil.

A milky appearance of your engine oil could be a sign that your head gasket is faulty and should be replaced as soon as possible.

Once you have noticed a milky engine oil and are sure that it is due to a bad head gasket, contact a marine mechanic as soon as possible.

Method 2: Repair Cracked Engine Block

A cracked engine block can cause water to get into your engine oil. The cracks in the engine block will allow a passageway of the antifreeze fluid into the engine oil, causing a milky appearance.

Contact a marine mechanic as soon as you notice a crack in the engine block.

Method 3: Clean the Reservoir Regularly

Leakage of coolant into the combustion chamber will cause milky engine oil. This can cause the engine to run higher than usual and eventually lead to a blown head gasket.

To ensure the smooth running of the engine, it is important to clean the reservoir regularly.

If the condition is out of your control, contact a marine mechanic to change the reservoir.

Method 4: Use Flushing Oil

An easy way to get water out of engine oil is by using flushing oil. You can flush the milky oil in your boat engine with flushing oil.

When flushing the milky oil, ensure that the breathers are clean. After flushing, use a new oil filter and replace the flushed oil with a premium, high-quality engine oil.

You should perform to flushing process just before an oil change.

To flush your engine, you would need:

  • Oil pan
  • Engine flush additive
  • New oil
  • A clean rag
  • Ratchet and socket set
  • New oil filter

How to do this:

Flushing your engine is an easy process and does not require any technical skill.

Step 1: Bring the engine up to full operating temperature. This allows the oil to flow better.

Step 2: Turn the engine off and add the additive.

Step 3: Allow the engine to run for 10-15 minutes.

Step 4: Turn off the engine and change the oil as you normally would.

Step 5: Remove the drain plug and place the oil pan between it.

Step 6: Remove the old oil filter and replace it with a new one.

Step 7: Install the drain plug.

Step 8: Replenish the engine according to the specification.

Step 9: Start the engine and check for leakage.

Method 5: Use Premium and High-Quality Oil

The brand of engine oil contributes to the overall performance of the boat’s engine. You must use premium and high-quality engine oil for the smooth running of your boat’s engine.

A premium and high-quality engine oil can extend the life of your boar and increase its performance.

Method 6: Regular Inspection of your Boat

It would be best if you inspected your boat as often as you can. Some of these problems can be avoided if there’s regular inspection of the engine parts.

Also, it would be best if you had your marine mechanic inspect your engine regularly.

This would help detect faults in the engine parts before they cause severe damage. Regular inspection tells you when you need to change some engine parts.

Why is my Outboard Oil Milky?

The main reason your outboard oil would appear milky is when there’s water in the outboard motor oil.

  • Outboard oil would appear milky when there’s a stuck or missing thermostat. This stuck or missing thermostat can cause condensation in the cylinder walls due to extreme heat produced from the engine and cold water from the water pump. This condensed liquid will pass through the piston rings and get into the engine oil, which will make it appear milky instead of the normal light bronze or maple color.
  • Your outboard oil will appear milky when the piston rings are damaged. When the piston rings get damaged, it will allow fuel and exhaust to blowback into the oil, turning the oil into an abnormal milky color.
  • Your outboard oil will change from the light bronze or maple color into an abnormal milky color when you have a blown head gasket. A head gasket seals the combustion chamber in a boat engine. With a blown head gasket, every time the piston descends, it sucks water into the combustion chamber. The water will find its way down the piston rings and get into the oil.


Water can get into your engine oil and make it appear milky through various means. When this happens, most people would not know what to do and what necessary steps to take.

An appearance of milky engine oil is a sign that something is amiss in your engine that requires urgent attention to prevent further damage.

For example, a milky boat engine oil could be a sign that your head gasket is damaged and needs to be fixed as soon as possible.

A milky engine oil could also mean a severe crack in the engine block that needs to be fixed as soon as possible to prevent further severe damages.

Also, you must take your boat to a marine mechanic for regular inspection to prevent future damages to your boat.

When next you notice a milky engine oil, use any of the above methods for removing water from boat engine oil.