For 1977-2010 Mercury/Mariner 2-cyl, 8-40 Hp | 3-Cyl, 30-40 Hp | 4-cyl, 40 Hp outboards.
ID: 0.242″ | OD: 0.570″ | W: 0.164″

also crosses with:
Sierra: 18-7100-9
GLM: 45230
Mallory: 9-76509