If you’re going to change the oil, remember that the gear case is refilled in a rather nonintuitive way. There are two access screws to your engine’s lower unit, an upper (see photo above) and a lower. The lower access screw is found on the forward, lower end of the gear case, which is the bulbous section of the lower unit. To refill the gear case, use the manufacturer’s recommended gear oil, which can be purchased in squeeze tubes with a nozzle-type top. Insert the nozzle into the lower access hole and squeeze until oil seeps out of the upper screw hole. Next, insert and tighten the upper access screw. Then remove the nozzle from the lower screw hole and insert and tighten that screw. Make sure that both screws have O-rings on them; if the rings look crushed or worn, they should be replaced.