Virtual Tour – Part 7: Cleaver Revolution

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.

Dick Snyder

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.

Bob Hetzel

Kiekhaefer Aeromarine’s prop manufacturing included an in-house pattern shop where Tom Dauterman created prop mold “masters” out of wood.
A Mercury Racing Lab Finished 3-blade cleaver is featured in this 1976 photo of Team Mercury drivers Bill Seebold Jr. (L) and Reggie Fountain.

Bob has seen it all when it comes to propellers. Bob Hetzel retired from Mercury Racing in 2003 with 46 years of service; I gave him a call to catch up and get his input on prop history. Bob explained the first two and three-blade props were commonly referred to as “elephant ears” due to their rounded blade tips. These early stainless steel props were first developed for the 100 h.p. in-line six cylinder Mercury outboard. The progression from two to three blade props came out of tunnel boat racing. “We first started with low-rake props, higher rakes came later. The Team drivers were complaining about the stern of their boats getting loose in rough water races. We added a third blade which sucked the stern into the water. This greatly improved handling in rough conditions,” said Bob.  Bob couldn’t say for sure, but he thought the cleaver design was first developed in Italy. In 1995, Bob moved from Mercury’s Plant 38 in Oshkosh to the newly expanded Plant 36 in Fond du Lac shortly after the merger of Kiekhaefer Aeromarine with Mercury Performance Products.

A 4-blade cleaver as featured in the 1988 Kiekhaefer Aeromarine propeller catalog.
Fred Kiekhaefer watches craftsmen work their magic finishing Kiekhaefer Aeromarine propellers.

“With Brunswick’s 1990 acquisition of Kiekhaefer Aeromarine, we had to sort through both propeller lines to see what we all had. We checked each others products, manufacturing methods, etc. We came to the former Kiekhaefer facility with two prop lines. They had a much better infrastructure for making props. Their sterndrive cleavers were much better than ours. We had just started development of a 4-blade cleaver at the time of the acquisition. They were making three, four and five blade cleavers. It was obvious which line of sterndrive props we were going to keep,” said Bob. Fred Kiekhaefer added, “Mercury brought a wide offering outboard racing propellers to the party. We had none. Mercury also had a talented pool of racing prop technicians — and Bob! He has such a breadth of application experience. Guiding this critical aspect of our business through the merger was uplifting. Watching folks with their differing perspectives (but mutual respect) sift through one another’s products – thinking, learning and agreeing on winners and losers – confirms the value of genuine teamwork.

“It’s all the more interesting when one knows why Kiekhaefer Aeromarine got into the prop business in the first place: back in the early 1970’s, my father quit Mercury — the company he founded. (That’s another, long story.) Then, ‘Mr. K’ began making sterndrive components to beef up merCruiser’s for offshore racing. New Mercury management didn’t like that and refused to continue selling him parts – including props. So his pattern maker, Tom Dauterman, was directed to tool three bladed props…but stainless steel cleavers. Later, I acquired that tooling, hired Tom and the prop makers, and expanded the propeller line for surface piercing applications; Tom added more blades, blade thicknesses and rake angles — all within my company. When I sold to Brunswick, we came full circle.”

CNC in the Digital Age

This classic ad features powerful testimonials from some heavy-hitters in the performance boating industry.
The new Pro Finish CNC cleavers were developed to handle the monster torque of Mercury’s 1350 sterndrive.

The Kiekhaefer Aeromarine cleavers served us well. But like most things, they had a limited lifespan. The biggest challenge was inconsistency from one prop to another. A left-hand, counter rotation prop would be off in rpm from the right-hand mate. All of this would be addressed prior to leaving our facility, but corrections were labor intensive and a burden to continue. Advancements in multi-axis Computer Numerical Control (CNC) machining provided an opportunity to once again advance the quality and consistency of our high horsepower sterndrive propellers. Our exclusive CNC machining process enables us to produce perfectly matched sets for optimum boat operating efficiency and propeller durability. Our new Pro Finish CNC Cleavers fill the need for durable props that have the stamina to stand up to the big fat monster torque of the 1350 and M8 sterndrive.

This concludes our Virtual Tour series. Thanks for following us along. Please ask questions about this or any of the previous six tour posts.












Share Share

7 thoughts on “Virtual Tour – Part 7: Cleaver Revolution”

  1. This is a great article. We have many customers that come in and want to know more about the Mercury Racing Cleaver. We sell a couple a year and customers absolutely love them.

  2. I have a 21ft Wellcraft sport cuddy with a 260 merc sterndrive with a high 5 sst 21 pitch runs at 5900 rpm i think i could go to 23 pitch what would you recommend in a cleaver prop and what pitch? top speed right now is 52MPH GPS what gain would i get with a cleaver thanks.

      1. Al,
        I thought it might be a typo, thinking it was 4900. You will want to consider time to plane and your recommended engine operating rpm when contemplating moving up in pitch. You want to be sure the engine stays in its recommended RPM range at WOT.

    1. Al,
      Mercury discontinued the Cleaver style many years ago because it was a limited use prop. Many boats require bow lift to generate good performance. The Cleaver was designed to just push the boat forward with minimal bow lift. The Mirage took the place of the Cleaver. If you stay with the HighFive, the 23″ pitch should drop engine speed by 300 rpm and enhance top speed by 1.5 mph. However, planing performance might suffer, meaning it could take a little more time to plan.

  3. I have a old mercury 1250 (tower of power) and I am looking for a prop that will both maximize speed and efficiency looks to be currently running and O.E.M. style prop

    Motor is currently on a Switzer speed boat 18′

    1. Alab,
      Probably the Laser II 3 blade stainless steel propeller, the 19” pitch is part number 48-899004A46 and the 20” pitch is 48-16990A46.

Leave a Reply

Your email address will not be published. Required fields are marked *