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Steps for Changing the Oil on a Mercury 40-60hp Four-Stroke Outboard Motor


Oil is the life blood of any engine. That's why it's important to drain and replace oil whenever your boat will be unused for a significant period of time, particularly at the start and end of each boating season. Check your engine manual for recommendations on how often to change oil based on hours of operation, but always remember it's even more important to change oil when your boat is not in use to avoid acid and moisture from damaging engine parts.

Fresh oil extends the life of your engine, plain and simple.

The video above and the notes below are specific to changing oil on a Mercury brand 40-60hp four-stroke motor. Many of the principles are the same for other motors, but it's recommended to seek out the proper instructions for your specific engine.

Before changing oil, it's a good idea to run the engine a few minutes to let the oil warm up and flow, allowing any contaminates to move from the bottom of the pan. Let the engine cool before changing the oil, so you don't burn yourself on it.

Items needed:

  • Socket wrench
  • Oil-filter socket
  • Drain pipe
  • Oil-filter funnel
  • Clean rags
  • 4-stroke engine oil


  • Tilt the engine up to the trailering position.
  • Turn the outboard so the drain hole is facing downward.
  • Remove the drain plug and drain the engine oil into an appropriate container
  • Once oil is completely drained, lubricate the seal on the drain plug with oil and reinstall.
  • Begin changing the oil filter by placing a rag or towel below the oil filter to absorb any spilled oil.
  • Unscrew the old filter by turning the filter to the left.
  • Clean the mounting base and apply a small layer of clean oil to the filter gasket. Do not use grease.
  • Screw the new filter on until the gasket contacts the base. Then tighten three-quarter to one turn.
  • Remove the oil-fill cap and add oil to the proper operating level. For exact information on recommended engine oil and oil capacity, reference your owner’s manual or maintenance decal on your engine.
  • With adequate water supply, idle the engine for five minutes and check for leaks. Stop the engine and check the oil level on the dipstick. Add oil if necessary.

To find out more information on changing engine oil on Mercury outboards, refer to a Mercury owners manual or visit mercurymarine.com.