Marine propellers are described as a "mystic art." Meet Merlin and his magicians.
Skin-of-toad, eye-of-spider, a little stainless steel and presto, Merlin (aka Steve Powers) creates just the right prop.
The new 4-stroke outboards, in particular, are creating a demand for some solutions more sophisticated than are to be found on a propeller chart, or on-line propeller calculator. One complicating factor is that 4-stroke outboards tend to be heavier than their 2-stroke counterparts, which on some applications, can cause a myriad of new handling challenges. As a result, these boat buyers can be, both, disappointed and confused by their boat’s performance. The good news is that, in many of these instances, a simple change of propeller geometry can be the cure.
Peak performance gets complicated
Different owners have different expectations. Some want rocket-like hole shots, others want max top-end speed, or best fuel efficiency at cruise. We have tested boats that porpoise with the heavier 4-strokes, and our solution has been to simply put a smaller engine on the boat. Had we called PowerTech!, perhaps they may have been able to suggest a prop to solve the problem.
Like boats, all engines are also a compromise. They are designed by the factory to have peak performance at a certain rpm and load, with a gear ratio intended to take fullest advantage of the motor’s powerband. Since this gear ratio is fixed, a customer wanting something different, in terms of performance, may find that changing the propeller affords the best solution.
A special prop may be the best fix
Manipulating propeller geometry -- pitch, diameter, size of blade, number of blades, rake, shape of blade, cup in leading edge of blade, cup in trailing edge of blade, rolling edge, thin blade, thick blade, progressive pitch, heat treating and of course -- skin-of-toad -- all go into creating the best solution. PowerTech! does not weld blades on hubs, but uses the lost-wax, investment casting method using high-carbon, 15/5 stainless steel.
PowerTech! personnel are happy to talk about their favorite subject to help you find your best solution.
For more information go to the PowerTech! website at www.ptprop.com. or call 800-736-7767.