Cylinder liner

The cylinder liner is the replaceable cast-iron sleeve that forms the running surface of the combustion chamber and the seat for the piston rings. Marine liners are alloyed grey cast iron, often with a phosphorus network and honed surface to hold an oil film. The liner is a wear part: the bore is measured at overhaul and the liner renewed when wear reaches the maker’s limit, commonly about 0.6 to 0.8 percent of bore diameter. Top-end wear is driven by abrasive scuffing and cold corrosion from sulfuric acid condensing on the wall, which the alkaline cylinder oil neutralizes. Large two-stroke liners carry drilled lubrication quills and, in modern designs, anti-polishing rings.