Mercury 40 Service Manual page 466

Draining and Inspecting Gear Lubricant
If gear housing is installed on outboard, disconnect (and isolate) spark plug leads
from spark plugs before working near the propeller.
1. With gear housing in normal running position, place a clean pan under housing and
remove vent plug and fill/drain plug (with gaskets).
a -
b -
2. Inspect gear lubricant for metal particles (lubricant will have a "metal flake" appearance).
Presence of fine metal particles (resembling powder) on the drain plug magnet indicates
normal wear. Metal chips on the magnet indicate the need for gear housing disassembly
and component inspection.
3. Note color of gear lubricant. White or cream color indicates presence of water.
4. Presence of water indicates the need for disassembly and inspection of oil seals,
O-rings, gaskets, shift shaft boot and components for damage. Pressure check gear
case prior to disassembly.
90-828631R3 MARCH 1999
Vent Plug/Washer
Fill/Drain Plug/Washer
WARNING
a
b
NON-BIGFOOT GEAR HOUSING
Page 6A-11