andy wrote:
hi, i have bought a old red band 70's model merc 9.8 and want to cange
the gear oil. i find and remove the drain plug but can't find the
vent/fill plug. can anyone help as i am new to this? thanks

It should be on the starboard side just above the cavitation plate
about 5 inches back from the leading edge. On earlier models the vent
plug is sometimes smaller than the drain. I noticed you called it
vent/ fill. You don't ever want to fill the gearcase through the top
plug, this will trap air in the bottom of the housing and cause a lack
of lubrication. This can terminally damage your gearcase. Always fill
from the bottom plug till it comes out the top. You can use a pointed
cap on your gearlube bottle and squeeze it in or most marinas sell
pumps that screw into the bottom hole.