Tightening the top screw, at the wide end of the triangle of this Algonac (mindermanmarine.com) scissor puller, grips one edge of the propeller hub and also the center of the end of the propeller shaft. Tightening the other screw, at the narrow end of the triangle, separates the two arms. Leverage created where those arms pivot pressure the prop hub toward the shaft end. Two sizes cover props up to about 80 inches, but since pressure is exerted only on one edge of the propeller hub, not in line with the center of the propeller shaft as is the case with most pullers, Algonacs don’t work particularly well to pull stubborn props.
On many new propellers, blades protrude in front of the propeller hub enough that Walter or Pro-Pull plates ding the blades. Chains around blades might cause similar damage. Also, high-speed boats today may not have space between the propeller and strut to accommodate the plate of either a Walter or Pro-Pull puller, so the only option is the Pro-Pull using chains around the propeller blades. Algonac pullers also require clearance between the prop and strut.