For 1977-81/1985-89 Mercury/Mariner 1-cyl, 4-5 Hp outboards.
Hub uses key
ID: 11 mm | OD: 40 mm
W: 12.6 mm | 6 blades

also crosses with:
Sierra: 18-3073
GLM: 89860
Mallory: 9-45611
Parsun: ASP500325