go to wal-mart in the fishing section and get the lower unit oil -marine grade
you take out the vent screw and the drain screw and refill it from the bottom hole until it runs out the top (vent) hole to prevent air bubbles inside.
youll also need to change those little plastic washers on the screws or you may develop a leak i buy a bunch at a time from my boat store to have some on hand
you can also get it from this site and some kits comes with a pump, if you dont buy the pump you just squeeze the *&*%^&% out of it until it fills up out of the top hole
