Mercury Mariner V-250 V-275 Outboard Service Shop Manual 1990, Page 15Get this manual
Gear Housing Lubrication AWARNING
To avoid accidental .tarling, disconnect spark plug Ignition wires before working near the propeller
4Replace upper lubricant vent screw and washer and continue filling until excess starts to flow out of lower lu bricant vent screw holeNOTE: Lubricant will exit out at the top ve nt hole before exiting out of the lower vent hole due to the path it must take to exit tram the lower vent holeAfter lubricant has flowed from the top vent hole and that vent screw is reinstalled, allowing the air to exit tram the gearcase through the lower vent hole will facil itate the fill ing of the remainder of the gearcase with lubricantAfter lubricant is observed flowing from the lower vent holeallow the excess lubricant to flow freely from the lower vent hole unti it stops before installing the lower vent screw