Measure the large end bore and then the small end bore. Now measure the overall length of the hub. Subtract the small end diameter from the large end diameter. Divide the Hub length by the remainder to ascertain the taper eg.

Large End Diameter 1.00"
Small End Diameter 0.81"
1.00" - 0.81"= 0.19"
Hub Length 2.25"
2.25 / 0.19 = 11.842

Therefore the taper would be an imperial 1:12 taper.

Cavitation is bubbles of partial vacuum caused by excessive propeller speed or loading. When these vacuum bubbles implode on the suction side of the propeller, they do so with such force that it causes the metal to be pulled off the surface causing erosion and vibration.

The pitch is the theoretical distance that the boat travels with one full revolution of the propeller eg: 10-inch pitch would move the boat 10 inches.

Carefully following the diagram, position the propeller so that you can place the thumb of either hand into the bore, with your fingers as if you were going to pick up the propeller. If you are using your right hand and you can pick up the propeller it is right handed. However if you cannot get hold of the blade, then it will be left handed.

The D.A.R mentioned on all propellers stands for the 'Disc Area Ratio'. This represents the total of the propeller blades in comparison to the total area of the circle of the same diameter. All CJR propellers have their model name, so a 16 " Ultrafine .65 would have a surface area of 131 square inches.

16" CIRCLE.
Area = px(8x8) = 201
Area of Blades = (3 x 43.66) = 131
Shaded Area = D.A.R =100 / 201 x 131 = 0.65

N.B. D.A.R ( Disc Area Ratio) is also referred to as the B.A.R ( Blade Area Ratio)

Rake is the angling of the blades away from the centre line. Rake is used as a means of increasing clearance form the hull, reducing vibration and directing the thrust of the propeller.

Skew is where the contour of the blade is not symmetrical but swept back. This causes radial sections of the blade to enter the water sequentially instead of at the same time. This helps reduce vibration and increases efficiency by easing the transition of the blades from the full slipstream, away from the deadwood or bracket, to the slower slipstream in the shadow of the deadwood or bracket.