How To Change Your Outboard Lower Unit Oil

How To Change Your Outboard Lower Unit Oil

The lower-unit is vital to the over-all performance of your boat. Lubrication is the key factor in controlling the extreme pressure exerted inside an outboard engine’s lower-unit. The lower unit’s oil creates a film around the internal parts of the lower unit, avoiding high temperatures that can seize internal parts together and cause catastrophic failure. Not only damaging the lower unit, but also in some cases freezing the drive- shaft which causes damage to the power head. Regular maintenance allows hours of trouble-free enjoyment while prevent costly expenses of your boat.
Inspect the lower-unit following these steps:

  1. Remove the prop, check for any fishing lines cutting its way through the seal, clean the splines with a wire brush and apply marine grease to the prop. Torque according to specification and secure the cotter pin.
  2. Drain the gear case, place the outboard engine in a vertical operating position, place a drain pan below the outboard engine and remove the vent plug first, then the fill/drain plug.
  3. Check the gear lube for water intrusion and metal particles. If water is present, it will give the gear lube a milky color appearance. A small amount of metal particles indicates normal gear wear. The metal particles are normally collected on the

drain plug. An excessive amount of metal filings or larger particles may indicate abnormal gear wear. See a picture with water intrusion in the lower unit oil.

4. Fill the gear case with your manufacture recommended gear-lube. Slowly pump until the lubricant drains from the vent hole. Let the lubricant over-flow, in-order to prime air from the unit. Once all air bubbles have exited the gear case, screw-on the vent screw with a new washer/seal. Then, remove the gear-lube dispenser from the drain screw “quickly” and screw-on the drain/fill plug with a new washer/seal. Use a 5/8 flat head screw driver to torque well the drain plug.
Follow your schedule maintenance in the owner’s manual to extend the life of your outboard engine and time on the water. By maintaining your boat /engine at its peak performance you will $ave!

Happy Boating,
Jorge Alberto
JA Outboard Service
786-251-402 or contact us at

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