Yamaha Marine Gearcase Lube is designed for all Yamaha outboards (except V8 and V6 MAX SHO) and sterndrives. Its special rust and corrosion inhibitors protect bearings and internal components from the harshest saltwater marine environment. Use genuine Yamaha Marine Gearcase Lube at factory recommended service intervals for optimal gearcase lubrication. You fill a gearbox from the bottom drain plug so as to push all the air out the top drain hole. Replace top screw first when gearbox is full then remove filler and replace bottom screw.