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The lower units of outboard engines house such components as the shift linkage, bearings, water pump, gears and driveshaft. Problems with any of these parts can interfere with proper boat operation and require troubleshooting to resolve.
A milky or whitish color in the outboard engine lower unit gear oil indicates a water leak, which can lead to engine stalling or failure. Outboard engine lower unit leaks often result from a broken propeller seal. The operator should replace the seal and flush the oil to resolve the problem.
If the outboard motor slips out of gear, the shift rod linkage, or linkage connecting to the lever that allows the operator to manually change gears, may be to blame. Any damaged or worn components, such as the bushings or coupler, in the upper or lower shift rod linkage should be replaced.
If the outboard engine lower unit propeller sustains damage, often caused by hitting or pushing against an underwater obstruction, it can slip on its hub and cause impaired outboard steering. The operator should inspect both the propeller and hub for damage and replace them as needed.