How do you fix a lower unit oil leak in a mercury 9.9?

Answer 1

First, verify that the leakage you see is gear oil rather than fuel. Oftentimes, an engine that is running excessively rich, or has a weak ignition system, will appear to be leaking gear oil, when in reality, it is simply unburned fuel running down the exhaust and out the water drain holes or prop. In the case of gear oil leakage, the gearcase will need to be disassembled for inspection of shafts' and seal/o-ring replacement.