You've got a Quicksilver (Mercury) Black Diamond prop, 10.25" diameter, and 14 pitch.
Very common prop size, used for over 40 years.
It should fit these motors:
Mercury - Mariner Outboards. 25 to 70 HP
25 HP Bigfoot 4-Stroke All Years
30 HP 2 & 4-Strokes 1994 & Newer
35 HP 1984-1989
40 HP 2 & 4 Strokes (Not Bigfoot) 1977 & Newer
45 HP 1986-1989 48 HP Mariner All Years
50 HP 2 & 4 Strokes (Not Bigfoot) 1977 & Newer
55 HP 1995 & Newer
60 HP 2 & 4 Strokes (Not Bigfoot) 1978 & Newer
70 HP 1977-1983
It will also fit 1995 and newer 40, 50, and 70 hp Force motors.
And maybe some more motors. [h=1][/h]