Essential Maintenance
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Written By: Conor Twomey |
Posted: 26/06/2008 |
"the gear oil in the lower unit needs to be checked at least once midseason and then changed out at the end of the year."
On most outboard and outdrive lower units, the gearcase will have two screw plugs on the side of the gear housing. Some units have these screw plugs located in the hub just forward of the propeller, in which case the propeller must be removed before the gear oil can be changed. Here is how to change your lower unit's gear oil.
1) With the motor in an upright position, locate a drain pan to catch drips from both the LOWER hole and the tip of the lower unit. Remove the LOWER screw plug, at this point not much of that 90-weight gear oil will come out. But when you now remove the UPPER screw plug, it will begin to flow. Let the lube dribble out, allow at least 10 minutes for it all to drain out. Don''t rush this step. While the oil is draining you can check the condition of the "O" rings on the screw plugs and change if necessary. NOTE: Watch carefully for water. If water is found in the gear oil, then the lower unit needs attention. The presence of water will usually make the oil look milky. If there is water it indicates a bad seal, in which case, you should take it to your outboard dealer and have it checked for pressure and vacuum. Also, as the oil drains, carefully inspect it for excessive metal filings or discoloration, which are signs of excessive wear, and may indicate that it is time for a lower unit rebuild. Stirring a magnet through the oil should detect any filings. GEAR OIL CONTAINERS: EP-90 gear oil comes in several different containers. It may come in an oversized toothpaste-style tube or in a bottle with a built-in pump. I prefer the pump type.
2) After all of the old lube oil has drained out, insert the new lube oil tube into the lower screw plug hole and squeeze or pump oil into the gearcase until it oozes out the upper hole.
3) After a teaspoon of oil has flowed out of the top hole, install the UPPER screw plug and tighten it. This will form a vacuum at the top of the lube sump, so that it won''t drain out when you remove the tube from the lower hole.
4) Now, remove the lube oil tube from the bottom hole and immediately install the LOWER plug. Tighten it.
5) When the bottom screw is fully tightened, again remove the UPPER screw plug. This will allow the lube oil trapped in the sump to settle and level out, permitting any bubbles to float to the top of the oil. Allow the motor to stand upright for another hour while the bubbles work their way to the top.
6) Recheck the oil level and add oil to the UPPER hole until the oil is level with the base of the threads.
7) Reinstall the UPPER screw plug and tighten. NOTE: Do not use non-marine gear oil, as supplied by auto parts stores. Special outboard gear oils have a water-dispersant additive that is not present in automotive gear oils. Also, not all outboard lower units use gear oil; some require regular four-stroke engine oil, and others use a marine grade of automatic transmission fluid. Check the specifications for your outdrive.