How to Change Your Mercruiser Engine Oil

Changing your Mercruiser engine oil is not as difficult as you might think. Having the right tools makes this job much easier.

Steps

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    Read your Owners Manual and its Safety Precautions.
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    In general, you need to change your oil every year or every 100 hours of use, whichever comes first.[1]
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    Visually inspect your engine and check the oil before starting.
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    Make sure the prop has been removed and that no people or pets are near the stern drive or prop before starting the motor.
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    Check for fuel or fuel vapors outside or in a well ventilated area to prevent Carbon Monoxide poisoning to people.[2]
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    Make sure your engine has a water supply before starting.
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    Be prepared for spilt oil. Cover your floor and cushions with old towels or blankets.
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    Start your motor and let it warm up. This will warm up the oil and make it much easier to suck it up and out of your dipstick tube.[3]
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    Turn the motor Off. After the engine has run long enough to reach operating temperature turn the motor off and let it cool for a few minutes.
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    Remove the dipstick and thread the oil hand pump onto the end of the dipstick tube.[4] If you are using an electric oil changer bucket hook up the hose to the tube and attach the pumps wires to the battery (red is positive and black is negative).
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    Suck out your oil into a container. Mer cruiser dipstick tubes are also Oil Withdraw tubes. You can suck all the oil out of the engine through the dipstick tube. This requires the use of either a small hand pump (part 802899A1 Oil Pump which can be purchased online or you can buy a more expensive Oil Changer Pump/Bucket Assembly from a marine supply store (about $160.00 and up).
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    Replace the oil filter.
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    Use the correct filter wrench and remove the old filter. Turn it counterclockwise as viewed from the bottom end of the filter. In some cases the filter might be difficult to remove. This is usually because it had been over-tightened when installed. A good wrench and patience usually prevails but in some cases you have to drive a large screwdriver through the body of the filter to get it off.
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    Once the filter is removed use a lint-free towel and wipe off and inspect the filter mounting area. Make sure that the old filter o ring has been removed from the engine.
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    Compare the size and type of the threaded hole of the new filter to the old filter to make sure you have the correct type.
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    Coat the o ring on the new filter with clean oil.[5]
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    Thread the new filter into place until hand tight.
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    Use the filter wrench to tighten another 3/4 of a turn and no more! Over tightening the filter makes it very difficult to be removed.
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    Look up your engine oil capacity in the owner's manual or on the capacity decal on the engine. Most inline 4 cylinder engines take 4-5 quarts.[6] Most V6 engines take about 5 US quarts (5,000 ml). Most V8 small blocks take about 5 US quarts (5,000 ml) and Big Block V8's can take up to seven quarts depending on the exact model.
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    Fill the engine with the correct amount of oil.[7] Newer Mer cruiser engines use a Color Coding System to locate and identify the oil fill cap and dipstick. Mer cruiser uses yellow to identify oil service points.
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    Let the motor sit for 5 minutes before checking the level on the dipstick. This will allow the new oil to drip all the way down into the oil pan.
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    Remember that the filter will hold some oil too.
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    After you are done filling install your oil fill cap and perform a general inspection on the engine. Make sure the filter has been installed and that you have cleared the engine area of all rags and tools.
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    Supply a water supply to the motor and start the engine.
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    Immediately inspect the oil filter while the engine is running. Look for any oil leaks. Go to the helm and observe your oil pressure gauge for a proper reading.
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    Let the engine warm up to operating temp.
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    Turn off the motor and let it sit for 5 minutes.
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    The manual that came with my mercruiser says to check the oil level with the boat "at rest in the water".
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    Remove and wipe off the dipstick and check the oil level again.[8]
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    Add more oil if needed. In general one quart adds about 3/8" on the dipstick. This can vary from model to model, though.
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    Clean up your mess and go boating!
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Community Q&A

  • Question
    What weight engine oil should I use in a 1996 4.3 Mercruser Alpha 1?
    Aloha27
    Aloha27
    Community Answer
    If the average high temperature where you live is about 80F, use 10W30. If the average high temperature where you live is about 90F, use10W40.
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Warnings

  • Use protective gloves.
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  • Use protective eye-wear.
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  • Props are sharp and can injure or kill a person or pet. Remove your prop before running the engine on land.
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  • Moving parts can injure or kill you. Always stay clear of moving parts such as pulleys and belts.
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  • Fuel vapors can explode causing damage, injury or death.
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  • Lead-Acid batteries can produce explosive hydrogen gas. Make sure the area is fully vented.
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  • Have a fire extinguisher close by, just in case.
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  • Warm engines can have hot spots which can severely burn you. Take care when working around hot engines to prevent burns.
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  • Always have an adequate water supply to your motor when running. Never run dry!
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  • Use care in working around a hot motor. You can be burned.
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  • Carbon Monoxide is deadly poisonous and impossible to detect by sight or smell. Only run your engine outdoors and clear of any buildings where people might reside.[9]
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  • Oil is known to cause cancer.[10] Do not get oil on your skin or in your mouth. Immediately wash off any oil with soap and water. Seek medical treatment if needed.
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Things You'll Need

  • Owners Manual (can be purchased at http://www.sterndrive-information.com)
  • Oil Filter Wrench (proper size).
  • Oil Changer Pump (hand or electric).
  • New Oil Filter (use engine serial number to look up).
  • Oil. Correct type and amount. See Owners Manual or decal on the motor.
  • RAGS, RAGS and more rags.
  • Water supply to motor.
  • Soap and Water.
  • Protective gloves.
  • Eye Protection.
  • Fire Extinguisher close buy.


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References

  1. ↑ http://www.boatus.com/boattech/casey/changing-engine-oil.asp
  2. ↑ https://www.cdc.gov/co/faqs.htm
  3. ↑ https://youtu.be/z0iexw1mYWg?t=52
  4. ↑ https://youtu.be/z0iexw1mYWg?t=105
  5. ↑ https://youtu.be/z0iexw1mYWg?t=198
  6. ↑ https://www.youtube.com/watch?v=ORvoSFrfetQ
  7. ↑ https://youtu.be/z0iexw1mYWg?t=250
  8. ↑ https://youtu.be/F0UjuwQ3-4E?t=332
  9. ↑ https://www.cdc.gov/co/faqs.htm
  1. ↑ https://www.cancer.gov/about-cancer/causes-prevention/risk/substances/mineral-oils
  2. Sterndrive-Information.com - Mercruiser parts, tools and information

About This Article

wikiHow is a “wiki,” similar to Wikipedia, which means that many of our articles are co-written by multiple authors. To create this article, 22 people, some anonymous, worked to edit and improve it over time. This article has been viewed 316,334 times.
75 votes - 92%
Co-authors: 22
Updated: October 21, 2021
Views: 316,334
Categories: Boats
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