How to Change Your Mercruiser Gear Lube

Properly maintain your Mercruiser sterndrive. Change the lube every year or sooner if you suspect a problem.

Steps

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    Determine what model drive you have.
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    Read your owners manual.
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    Buy the correct amount and type of lube plus a little more.
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    Buy a little hand pump that fits the bottle of lube to fill the drive.
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    Place a clean oil drain pan under the drive to catch the old lube as it drains out of the bottom of the drive.
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    Use a large screwdriver and remove the lower drain plug.
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    Remove the top oil vent plug.
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    Let the unit completely drain.
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    If your drive has an internal drive lube monitor bottle in the boat, remove the bottle from its bracket and pour out the old lube. Look in the bottom of the bottle. If you see residue in the bottom of the bottle it should be removed and rinsed out with carb cleaner or Power Tune. Make sure the bottle is clean and dry.
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    If the old lube looks and smells bad it could be an indication of a problem.
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    Inspect the gear lube for evidence of metal particles or water intrusion.
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    If the lube looks bad and you suspect a problem, FIX the problem before placing the drive back into service.
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    If the lube was simply old and smelly it is a good idea to flush the drive one time with new clean lube.
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    To flush the drive fill the drive from the BOTTOM hole with enough lube to fill the drive and then let it drain out fully. Do NOT reuse the flushing lube.
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    Use a sharp pointy pick and make sure to remove the old drain plug gaskets from the drain and vent holes. Never reuse an old drain plug gasket. Old gaskets get brittle and hard as rock. Look closely in the hole and use the pick to make sure all of the old gaskets have been removed. Buy new drain plug gaskets and place them over the cleaned-up plugs.
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    Fill the drive from the bottom-up until the lube flows out of the top/side vent hole.
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    Install the top vent plug with the new gasket and tighten.
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    If your drive has an internal drive lube monitor bottle, continue to pump lube until there is approximately one inch of lube in the monitor bottle. If you don't, the upper unit will not be lubricated properly.
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    Remove the lube fill pump from the bottom hole and quickly install the bottom plug with its new gasket.
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    Wipe up any residual oil.
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    If your drive has an internal drive lube monitor bottle, add lube to the bottle up to the "full" line. Be aware that the drive might have an air bubble and that the system might "burp" after being run. This could result in a drop of the oil level in the bottle. Just top off the bottle with clean lube and keep an eye on it. Be sure to loosen the bottle cap to avoid creating pressure in the system. Pressure in the system will make a mess when the hand pump fitting is removed from the bottom fill hole.

Tips

  • Water in the drive lube has a milky appearance.
  • Locate your drain plugs ahead of time.
  • Make sure the drive is in the full DOWN trim position.
  • Replace any damaged drain plugs.
  • Water in the drive lube will ruin your drive.
  • Use factory lube.
  • Have lots of good rags.
  • Bravo One and Two drives have to have the prop removed to access the drain plug.
  • Have a clean work area.
  • Stuck drain plugs can be removed with an impact screwdriver.
  • It's a good idea to remove the drive each season for an inspection of the gimbal and to check engine alignment.
  • Have your tools ready.

Warnings

  • Dispose of old oil properly.
  • The drive might be pressurized and the oil can spray out and get in your eyes. Use safety glasses.
  • Oil can be harmful in absorbed through your skin so use gloves.
  • Double check that you tightened the plugs securely.
  • Remove the prop for safety
  • Disconnect the battery negative before removing the prop.

Things You'll Need

  • More than enough factory recommended lube.
  • A small plastic lube fill pump to fill from the bottom hole.
  • Large wide screwdriver.
  • Oil drain pan.
  • New drain plug gaskets.
  • Rags.

Article Info

Categories: Boat Motors and Marine Engines