Sierra 18-2415 Lower Unit HousingSierra replacement lower unit housing for Gen II engines. Sierra aftermarket engine parts are manufactured to meet or exceed OEM requirements. For ratios: 1:47:1, 1:62:1; Fits: Gen II (1998 & Up) S/N (0L100040 & Up); Use with: 18-2400 Complete Lower Unit AssemblyInterchangeable with: Mallory; 9-79126; Mercruiser Stern Drive; 1623-815822A36;