Merc owners manual says ...
Remove both vent plugs (top two) , Remove bottom plug (let old grease drain) , Fill from bottom drain until grease comes out first vent hole (one to the rear) put plug in, continue filling until excess come out other vent hole, Replace other plug.
Drain one ounce out and replace lower plug.
Just wondering because trapped air from the top is the same as trapped air from the bottom ... Isn't it ?
Just wanna start a fight ... LOL