How to Change the Lower Unit Oil in My Johnson 48 SPL Outboard Motor

by Will Charpentier

An oil change may sound like a messy affair, but you can change the lower unit oil in your Johnson 48 SPL outboard motor with minimal fuss. You need an approved container in which to catch the oil you drain from the unit. You also should remember that turning a screwdriver clockwise tightens a screw, while turning a screwdriver counterclockwise loosens it. Dispose of the oil you drain from the lower unit properly.

Tilt your motor down with your power trim/tilt control, until the motor is level, to allow the gear lubricant to settle at the lowest part of the lower unit. Ensure the motor is level from side-to-side.

Slip a basin under the bottom of the motor to catch the oil as it drains from the lower unit. Loosen the drain/fill plug on the bottom of the lower unit with a screwdriver, and remove the plug. Rub the magnetized end of the plug between your thumb and forefinger, feeling for bits of metal. Small metal shavings are common, but chunky feeling bits of metal indicate a problem that requires your dealer's assistance.

Loosen the vent plug on the upper part of the side of the lower unit and remove it. Visually inspect the oil as it drains into the container below the lower unit. Outboard manufacturers warn that oil that has a milky appearance is contaminated, indicating that the propeller shaft seal has failed. Allow the oil to drain completely.

Replace the small washers on both the drain plug and the vent plug. Push the tip of the tube of gear lubricant into the drain/fill hole and squeeze the tube to force the lubricant into the lower unit. Watch the vent hole and, when you see lubricant coming from the vent hole, leave the lubricant tube in place and screw the vent plug into place with your fingers. Tighten the vent plug with the screwdriver.

Pick up the drain/fill plug and pull the lubricant tube from the drain/fill hole. Thread the drain/fill plug into place with your hand and tighten it with the screwdriver. Wash down the exterior of the lower unit with liquid dish detergent and water to remove any lubricant that may have spilled out.

Items you will need

  • Basin
  • Screwdriver
  • Vent/Drain plug replacement washers
  • Gear lubricant
  • Liquid dish detergent
  • Water

References

  • "Johnson Repair Manual -- 2.5 to 250 HP Models, 2002-2007;" Seloc Marine; 2007

About the Author

Will Charpentier is a writer who specializes in boating and maritime subjects. A retired ship captain, Charpentier holds a doctorate in applied ocean science and engineering. He is also a certified marine technician and the author of a popular text on writing local history.