Helices Pirania, con Palas Intercambiables

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Bent Into Shape

Story and photos by Randy Scott

Piranha Propeller's takes a big chunk out of potential repair costs with its new line of interchangeable props.

All boaters seem to have an innate propensity to protect their boat?s propeller. So when Brad Stahl, the owner of Piranha Propellers, tells you to deliberately drive his boat over a submerged 4-by-6-inch wood beam in a blatant attempt to damage the prop, it makes you a bit queasy ? like a child acquiescing to peer pressure to do something he knows he shouldn?t.

?Okaaay,? you say with a hint of guilt, ?in the name of research.? You push the throttle forward on Brad?s old 19-foot Ranger. The weathered boat, which would be nicknamed Thumper by the end of the test runs, has seen better days. Brad can?t remember how old his Ranger is, but ventures it dates back to the mid- to late ?70s. It still has the original 180-hp MerCruiser beneath the engine hatch, which is truly remarkable when you consider that Brad has used it to intentionally ?thump? logs somewhere around 1,800 times. He?s had to take a hammer and straighten things out a few times, but like the old Timex watch commercials, it takes a lickin? and keeps on tickin?. The zillion props he?s used haven?t fared so well, however.

Before the test run, Brad drops a couple of anchors to strategically hold the wood beam at propeller depth, with a couple of buoys bobbing above it to mark the position like the entrance gate to a slalom course. You build some speed, take careful aim and enter the gate in a manner that would make a tournament ski-boat driver proud.

Thwack! The prop hit its mark.

A chorus of cheers goes up from the shoreside audience of Piranha Props employees, as well as a couple of curious agents from Progressive Insurance. They applaud with all the enthusiasm of fanatics attending a demolition derby.

Instantly upon impact, Thumper develops a bad case of the shakes, indicative of a damaged propeller. But instead of dread, Brad has a wide smile. ?Sounds like a good hit,? he says with boyish enthusiasm. ?I think we may have damaged a couple of blades on that one.?

Thumper limps back to shore where Brad jumps out with a prop wrench in hand. ?Oh yeah, good hit!? says Brad. Two of the Piranha props? composite blades have large chunks out of them.

It?s a sight that would normally make a boater sick. But Piranha has taken the bite out of expensive prop repairs. If this had been a stainless-steel prop, you would be looking at either replacing it for somewhere between $300 to $600, or spending a sizable amount of money trying to get it fixed, all the time knowing that it would never perform the same again. If it had been an aluminum prop, the cost of repair or replacement would be less, but still sizable. With the Piranha props, however, the pain is minimal.

Brad quickly removes the prop assembly?s rear end cap, slides the damaged blades out of the slotted hub, slides in new blades, taps them securely in place with a mallet, reattaches the end cap, puts the repaired prop back on the shaft, and you?re ready to go boating again. The whole process takes less than five minutes. And the cost is less than $22 per blade. Equally appealing is that the repair can be done on site without a certified mechanic, so there?s not much loss of valuable recreation time.

Like a bunch of school kids caught up in a bad prank, they repeat the masochistic prop bashing a number of times. The results are always the same: broken blades that are quickly replaced in an unscathed hub.

Piranha Propellers manufactures its props from a fiber-reinforced plastic called Verton. According to Piranha, the glass reinforcement fibers produce a tensile strength and stiffness that is 15 percent higher than die-cast aluminum. Because the fibers are brittle and hard to fashion, however, Piranha combines the fibers with more malleable, energy-absorbing Nylon plastic resin. By design, the impact-absorption properties of the prop provide protection to the boat?s expensive lower unit. The blades are designed to break before anything else. The interlocking hub that holds the blades is virtually indestructible. Made with a 6061 T6 aluminum core encapsulated in Verton, Piranha Props backs its hubs with a lifetime warranty.

The patented Piranha prop has some obvious advantages over conventional aluminum- and stainless-steel counterparts. For one thing, boaters finally have a simple and inexpensive solution to propeller repair. Rather than carrying a second backup prop, you can just bring along extra blades. And the ingenious blade-replacement design makes it quick and easy to repair, even in the field. Another advantage is that you can change prop pitch without carrying a separate prop; all you need are different pitch blades. So if you want to spend the morning skiing, you can use one set of blades, and when you want to cruise along at a higher top speed, you can simply swap the blades out.

Stowability is another factor with the Piranha prop. The blades take up hardly any room. Even if you want to carry an extra hub in the unlikely event that you?ll need to take Piranha up on its lifetime warranty, stowage space is minimal when you leave the blades unattached from the hub. Finally, a Piranha composite prop weighs half that of an aluminum prop and is six times lighter than stainless steel, which in addition to being easier to lug around, is also easier for the drive to spin it. Every boater should consider adding a Piranha prop to their gear bag.