Changing Lower Unit Gearcase Lube

Changing Lower Unit Gearcase Lube
Tiny metal particles are expected on drain plug magnets.

Changing lower unit gearcase lube is not expensive and pays huge dividends. Start to finish takes only about twenty minutes. Manufacturers offer gearcase lube pumps as part of their parts and accessories packages; average price is $11. Fluid is sold by the quart, prices range $8 to $18/quart.

Lube change process: 1) Remove prop nut and discard locking components. 2) Remove prop and hardware. Caution – blades can be sharp! 3) Remove lower and upper drain plugs. Discard plug gaskets. 4) Drain lube; engine position straight down, then tilted slightly forward. 5) Begin re-filling gearcase from bottom until fluid runs out the top. Let sit a few minutes for the air to settle. 6) Place new gaskets on plugs and install top plug first. Disconnect lube pump and quickly install lower plug. 7) Apply waterproof grease to prop shaft; install hardware, prop, and new locking hardware.

When the prop is off, inspect the hub for looseness, inspect shaft splines for twisting, examine old oil for milkiness (water contamination), and check for metal particles on drain plug magnets. Tiny, hair-like shavings are normal, metal shards are not expected.

Dispose of used oil responsibly. We recycle at CBM.

Thank you, and have a great spring season on the water!

Chris Mapp
Coastal Bend Marine
Port O’Connor, TX