Tapers - charts and how to measure

You can measure the taper bore of a propeller with digital vernier calipers.

Measure the small end to the taper inside diameter of propeller - nut end I.D. ( inside diameter)
Measure the large end to the taper inside diameter of propeller - front end I.D. ( inside diameter)
Measure the overall length of the boss (hub) of propeller Measure the keyway width.

Check how the old prop fits the taper shaft and the amount of draw - i.e. the overhang distance at the nut end so the prop tightens on the taper properly.

Propeller tapers are often not to any standard which makes this game a challenge. There are 4 common tapers used - 1 in 10 , 1 in 12 , 1 in 16 and 1 in 20 and then there are odd back yard ones.

Also check and confirm PROPELLER ROTATION - L/H or R/H - A Right hand propeller rotates clockwise when viewed from astern facing forward. A Left hand propeller rotates counter clockwise when viewed astern facing forward.
On a twin screw vessel the left hand prop is normally fitted to the port side.

S.A.E. Specification J755
The most widely followed dimensions for tapers is the internationally accepted standard S.A.E. taper dimensions which is 1 in 16 up to and including 5 1/2" diameter. Above this diameter the taper is 1 in 12. This standard is incorporated in the American Boat and Yacht Council (A.B.Y.C.) rules which are commonly used in Australia. All dimensions for S.A.E. taper standards are based on the SMALL end of the taper. The reason for this is so propellers with different hub lengths (i.e. different diameters at the large end of the taper bore) will fit the same shaft diameter and have the nut face in the same position on the shaft.

1 in 16 taper is 3/4" inch to the foot and the angle center line is 1 degree 47' minutes 23" seconds.
1 in 12 taper is 1" inch to the foot and the angle center line is 2 degrees 23' minutes 9" seconds.

S.A.E. Specification J755 (unit: inches)

Propeller Hub Taper 1:10   ISO 4566:1992(E) (unit: mm)