When & How to Change Outboard Motor Oil

An outboard engine with contaminated or too little oil will wear out, seize up and eventually die.

Outboard engine oil change tips

To ensure the health and longevity of your outboard, you should check the oil level before every outing, and change the oil and filter on a regular basis. How often you need to change the oil on your outboard engine depends on how you use it.

When to Change an Outboard’s Engine Oil

Oil lubricates and cools the motor, and if it can’t adequately perform these tasks, it’s time to change it out.

Outboard motor oil change

Engine oil breaks down and loses its lubricating properties as it gets heated repeatedly. Fresh oil sports a pale golden color, while broken down oil is dark brown or black. Oil catches and suspends within it tiny metal fragments that get worn off the engine’s moving parts. Fresh oil is translucent and contains no impurities, while oil that needs changing is opaque and has a gritty texture when rubbed between your fingers.

Your outboard’s owner’s manual gives you the manufacturer’s recommendations for oil changes, but use that as a guideline for the bare minimum. Before every boat ride, pull out the dipstick and check the oil. Obviously you’re making sure the oil level is correct, but also check if the oil is dark and discolored, and put a drop on your fingers to feel for tiny metallic particles suspended in the oil.

The owner’s manual might say the oil needs changing every 50 hours. However, if the oil is showing signs of breaking down or is over-saturated with metallic debris, it’s time to change it out, even if the engine hasn’t yet run for 50 hours since the last oil service.

Additional Times to Change Outboard Oil

Engine oil also experiences chemical breakdown when left unused. The oil sitting in an engine that isn’t run for a couple of months or has been winterized will break down and lose some of its lubricating properties, which is why you should change it even if it’s in storage or inactive.

Outboard motor oil change tips

Moving parts within new outboard motors experience higher wear rates for the initial hours of running as they bed themselves in against one another. This extra wear produces higher quantities of metal fragments, so change the oil in a brand new outboard after approximately every 20 hours of use for the first 100 hours of running.

How to Change an Outboard’s Engine Oil

After buying the oil and a new oil filter, get a wrench or flathead screwdriver, some shop towels or rags and a drain pan. Run the outboard for a minute before changing the oil to warm the used oil, which makes it less viscous and helps it drain out faster. 

Step 1. Tilt and turn the motor so the drain screw is facing downward. 

Outboard engine oil drain bolt

NOTE: Depending on the outboard and the position of the drain screw or bolt, this may mean titling the outboard fully up or down, or tipping it to one side.

Step 2. Remove the top cowling to access the powerhead, then take off the oil filler cap to help the motor vent, which also allows the oil to drain out faster.

Outboard motor oil filler cap

Step 3. Place a drain pan under the outboard to catch the used oil as it drains out.

Outboard motor oil drain

Step 4. Remove the oil drain screw or bolt and its washer or O-ring with a wrench or flathead screwdriver. 

Outboard oil change drain bolt

NOTE: The drain screw/bolt is usually located on the side of the outboard, just above the lower unit.

Step 5. Inspect the drain screw or bolt’s washer or O-ring as the old oil drains out, and replace it if it’s worn.

Step 6. Reinstall the oil drain screw/bolt and its washer or O-ring, and wipe away any oil from the lower cowling and the lower unit.

Step 7. Tilt the outboard to the vertical position (if it isn’t already).

Step 8. Put a shop towel or rag under the oil filter to catch the oil that spills out when the filter is removed. 

Outboard engine oil filter change

NOTE: The oil filter is usually located on the side of the powerhead toward the bottom.

Step 9. Unscrew and remove the old oil filter. Use an oil filter wrench if it’s too tight to unscrew by hand.  

Step 10. Lightly coat the new oil filter’s O-ring with fresh motor oil, then install the new oil filter. Hand-tighten the filter first, then give it an additional 3/4 of a turn. 

Outboard engine oil filter ring

NOTE: Never over-tighten the filter, as it’ll be very difficult to remove during the next oil service.

Step 11. Fill the engine with marine engine oil. Your outboard’s owner’s manual will tell you how much oil the engine requires.

Outboard engine oil change how-to

Step 12. Reinstall the oil fill cap and run the motor on idle for a minute to distribute the new oil throughout the engine. Next, shut off the motor and let it sit for a couple of minutes so the oil can settle.

Step 13. Check the oil level on the dipstick, then top it off if necessary and reinstall the top cowling.

Outboard engine oil fill marker

 
FILTER Oil
Mercury

FILTER Oil

Qty.
OIL SYN 4-C @6
Mercury

OIL SYN 4-C @6

Qty.
WRENCH-FILT @2
Mercury

WRENCH-FILT @2

Qty.

 

Why Boats.net?

Commercial Discounts

Special discounts for companies in the marine industry

Details

Government Sales

Discounts for federal and most state and municipal agencies

Details