Merc Outboard Lower Unit Hole / Vent Question

[Gearhead62]

I am changing the gear oil in my relic - Merc '66 35 HP outboard.

3 plugs total on drive - Drain hole at bottom is normal, but I have 2 plugs up top: 1) metal - same as lower, and 2) plastic - larger than metal plugs and a bit higher than the other top hole.

Which one is vent hole? What is function of larger plug?

Thanks

 

[OldMercsRule]

Re: Merc Outboard Lower Unit Hole / Vent Question

I am changing the gear oil in my relic - Merc '66 35 HP outboard.

3 plugs total on drive - Drain hole at bottom is normal, but I have 2 plugs up top: 1) metal - same as lower, and 2) plastic - larger than metal plugs and a bit higher than the other top hole.

Which one is vent hole? What is function of larger plug?

Thanks

Metal plug is the vent.

Plastic is the water pump flush.


Hope that helps. JR

 

[Gearhead62]

Re: Merc Outboard Lower Unit Hole / Vent Question

Thanks - That's what I was looking for