1986+ Mercury 6/8/9.9/10/15HP 2-stroke Factory Service Manual, Page 258Get this manual
GEAR HOUSING
Filling Gear Housing with Lubricant
NOTE: Gear housing lubricant capacity 6.8 oz(200 ml)IMPORTANT: DO NOT use automotive grease in the gear housingUse Premium Gear Lubricant or High Performance Gear Lubricant 1Remove any gasket material from "FILL" and "VENT" screws and housing2Install new gaskets on "FILL" and "VENT" screwsIMPORTANT: Never apply lubricant to gear housing without first removing "VENT" screw or gear housing cannot be filled because of trapped airFill gear housing ONLY when housing is in vertical position3Slowly fill housing through "FILL" hole until lubricant flows out of "VENT" hole and no air bubbles are present4Reinstall "VENT" screw5Remove grease tube from "FILL" hole and quickly install "FILL" screw52998