Mercury 90 hp outboard Model # 1090412AD

[Frogman1998]

My lower unit has three plugs. Vent, Oil Fill & Drain. Can I use magnetic type screws for all three?

[boats.net]

No only use the screw with magnet on bottom screw.

[mojorisin']

3 screws vs 2

I have only owned a few outboards and the first one, a 30 HP Mariner 1993 had a vent and drain screw. My newer Merc 75 HP 1999 has 3 as mentioned by the OP. Is the 3rd to allow fill using just the nipple on the quart jugs (not a hand pump from bottom hole) while having the bottom screw in place, then looking for fluid to exit the fill level hole?

I currently have a leak at the fill level hole and need drain and refill, I'm curious thats all.

Thanks much!!