August 6th, 2012
CNC machines produce our perfectly matched 5-blade or 6-blade cleaver propellers.
Skilled craftsmen hand-finish each CNC prop.
Continuing from Virtual Tour - Part 6: Propellers…we’ll review the evolution of surface piercing propellers, culminating with our amazing CNC Sterndrive Cleavers.
I first reviewed my classic literature collection for information regarding the evolution of surface piercing propellers. Copy from the propeller section of a 1972 Hi-Performance Mercury/MerCruiser Accessories catalog references our change from bronze to stainless steel that year. I sent Dick Snyder an e-mail to get his input regarding racing propeller history.
Three-blade “elephant ear” props on a quad 1250BP rig ready for testing at Lake X.
A 2-blade stainless prop on a merCruiser III drive. This drive was packaged with a 475 h.p. engine.
Dick Snyder was in charge of Mercury’s propeller engineering in the early ’60s. “When I took over prop engineering in the early ’60s, I had inherited nothing but low rake (6 degree), 2-bladed props. We had no racing or hi-performance props. “There soon came a time when I fell in love with 15 degrees of rake and 3-bladed props for the added smoothness and a little better acceleration. You typically would lose a small amount of top-end going from a 2-blade to 3-blade prop. The higher 15-degree rake allowed the props to “hold” at greater trim angles for enhanced bow lift and greater hull efficiency. This resulted with even greater top-end speeds than the lower rake 2-blade props,” Dick explained. In 1984, Dick was promoted to Director of Mercury Hi-Performance. So he promoted Bob Hetzel to run Mercury’s racing prop and gearcase shop. “We had quite an interesting development of stainless steel props for racing, followed by replacing bronze for stainless steel on our recreational props,” said Dick. Read the rest of this entry »
August 2nd, 2011
Rake is the relationship of the blade face and the propeller hub.
Rake is the angle of a propeller blade face relative to its hub. If the blade face is perpendicular to the hub, the prop has zero-degree rake. As a blade face slants back toward the rear of the prop, blade rake increases. Rake is either flat (straight) or curved (progressive). Most lower horsepower (“lower” by Mercury Racing’s reckoning) outboard propellers, like Black Max aluminum and Vengeance, have 15-degree rake and are designed to operate fully submerged to push a boat across the water. Typically, higher horsepower outboard and sterndrive propellers have a higher flat or progressive rake.
A good view of our CNC cleaver prop on a NXT1 drive.
A greater rake angle generally improves the ability of the propeller to operate in a ventilating situation. Ventilation occurs when blades break and re-enter the water’s surface — such as occurs with 1) a Bravo sterndrive installed with a high “X” dimension, 2) a surfacing drive (NXT1, NXT6 SSM or M8) or 3) an outboard installed or jacked high on a transom. In surfacing operation, higher rake can hold the water better as it’s being thrown into the air — deflecting it aft and creating more thrust. Read the rest of this entry »
October 27th, 2010
Team AMSOIL - Photo Courtesy Pete Boden Shoot2Thrill Pix
Bob Teague, throttleman/owner of the Mercury Racing 525 EFI-powered Team AMSOIL Super Cat Lite offshore race boat, recently won two consecutive offshore races with the new props. Read the rest of this entry »