Mercury Mariner Outboard 225 3 Litre Service Manual 1994, Page 19Get this manual
SALT WATER CORROSIONGEAR HOUSING, BEARING CARRIER AND COVER NUT
Salt water corrosion buildup can be sufficient to split gear housing and destroy an entire lower unitTo protect against such damage, it is recommend ed that the gear housing bearing carrier and cover nut be lubricated on regular basis, as follows:
Service first at the 20-hour inspection, then on an annual basisRemove the cover nut and entire bearing carrier to adequately clean corrosive deposits and dried-up lubricant from both ends of the bearing carrier, as well as the gear housing internal threads and cover nut external threadsApply Quicksilver Special Lubricant 101 or 2-4-C Marine Lubricant to the ends of the bearing carrier and to the gear housing and cover nut threads, then reassemble and retorqueRefer to gear housing disassembly and reassembly (SECTION 6)