Mercury - Oil Change Kit, 15/20HP FourStroke, 1 Liter Maintenance 8M0081914. Overview. The little 15 and 20HP Mercury FourStroke carb motors are simple and reliable, but they absolutely depend on clean oil. They run warm, they get used hard on small boats, and they don't have a lot of extra lubrication margin. This kit gives you everything you need to knock out an oil change without hunting for parts-one bottle of the right marine oil, the correct filter, a new drain plug seal, and a drip tray s