Gear oil - filling from bottom ? - wondering (Yamaha F100 DET outboard)

Hi,

has some of you also wondering why gear oil should be filled from the bottom and pumped upwards ? - i think this method is a little bit strange and difficult.

Why not the same principle as filling engine oil ?

I would just hear your opinion.

[Aleutianwest]

Gear oil

Filling from the bottom gives minium chance of any air pockets in gearcase

[501nmc]

Its easier to not overfill the gearcase. Overfilling wouldn't allow the fluid to expand causing premature seal failure. Its also easier to see how much you've put in instead of guessing.