How to change outboard gear oil

Written by cameron easey
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How to change outboard gear oil
Outboads use oil that needs to be changed regularly. (fishermen image by pearlguy from

Changing the gear oil on your outboard is part of the yearly maintenance that needs to be done before the start of the season--to keep the motor running properly. Oil is used in multiple places, which can include the gear oil that is stored in the lower unit of the outboard. You can have a boat mechanic change the gear oil on your outboard or you can do this task yourself.

Skill level:

Things you need

  • Screwdriver
  • Drain pan
  • SAE 90 weight motor oil
  • Squeeze bottle

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  1. 1

    Take the boat out of the water and move it to an area where you can access the outboard.

  2. 2

    Set the outboard in a vertical position. This can be done by adjusting it manually or by using the trim tabs.

  3. 3

    Place a drain pan underneath the bottom of the outboard.

  4. 4

    Locate the vent screw and drain plug on the outboard. The drain plug is the one that is on the bottom of the outboard.

  5. 5

    Unscrew the drain plug first and then unscrew the vent plug. This will release pressure and allow the oil to flow out.

  6. 6

    Wait for all of the oil to drain from the outboard's lower unit. The oil may take up to 10 minutes to completely drain.

  7. 7

    Pour a quart of SAE 90 weight motor oil into a squeeze bottle.

  8. 8

    Insert the bottle into the drain hole at the bottom of the outboard. Squeeze the bottle to fill the lower unit with oil. Continue filing oil into the lower unit until it begins to come out of the top vent.

  9. 9

    Tighten the vent screw while leaving the drain hole plugged with the squeeze bottle.

  10. 10

    Remove the bottle and then quickly tighten the drain plug.

Tips and warnings

  • Let the outboard set out in the sun to heat up the oil in the lower unit.
  • If the motor is not completely vertical the oil will not drain out completely.

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