Keeping Barnacles Off Your Propeller

Having been plagued by barnacles and other intrusive organisms for generations, the sailing community has brought the full breadth of its considerable inventiveness to bear on this sticky problem.
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Somewhere under those barnacles is a shiny folding propeller

Somewhere under those barnacles is a shinyfolding propeller

From the moment we left the mooring, I knew what was wrong. The boat had sat, hardly used, for nearly a month; now, as I opened the throttle, the engine note changed to a complaining rattle, black smoke belched from the exhaust, and the boat moved reluctantly off as if tethered to the bottom by an elastic band. From past experience, I knew the propeller was covered in barnacles. The only bright note was that it was late October and we were taking the boat to be hauled out, so there would be no plunging into frigid New England waters to scrape the growth off the prop.

The problem of keeping your prop barnacle-free is by no means restricted to the Northeast. From the Florida Keys to the Bering Strait, those pesky arthropods alight gleefully upon your running gear and settle down for the long haul. And in another example of life’s little injustices, they affect us sailors more than they do powerboaters. The more you use your engine, the less likely you are to have your prop colonized by barnacles.

Having been plagued by barnacles and other intrusive organisms for generations, the sailing community has brought the full breadth of its considerable inventiveness to bear on this sticky problem. You’ll hear barroom tales of the efficacy of potions of waterproof grease mixed with cayenne pepper, tetracycline and even quinine powder; some swear that rubbing a black magic marker onto the propeller blades keeps growth away; and others hold forth about the growth-repellent properties of lanolin. All of these, according to the anecdote, have worked for some sailors in some waters at least some of the time. Just as with any bottom paint, though, there are many variables affecting the way your prop potions work—temperature, salinity, vessel movement, currents, sunlight.

Technique is critical when applying Propspeed

Technique is critical when applying Propspeed

And therein lies the twofold problem with propeller fouling. There is no clear consensus as to what works best in any given scenario, and even if something does work, how well will it adhere to a spinning propeller? Many different approaches have been tried: here are some of them.

Nothing at all: Some sailors polish their props to a mirror gleam and leave it at that, trusting the slick surface will offer no toehold to inquisitive barnacles. It seems to work sometimes; but often it does not. It never has for me.

Rub-on coatings: Some boat owners report that an easily applied polish like Sex Wax, beloved of surfers everywhere, works well and can be reapplied underwater. Diaper rash cream containing zinc oxide also has its, er, adherents. The case for magic marker is not convincing; if anyone has more than anecdotal evidence regarding this, please let me know. Lanolin—which keeps sheep from becoming waterlogged—also has its fans, and an effective proprietary compound called LanoCote, marketed as a propeller antifoulant, is available on the U.S. market.
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Antifouling paint: Bearing in mind that you should not use copper-based AF if your boat has a saildrive leg, this seems to be as an effective a method as any, and perhaps better than most. The trick is to sand your precious prop, and then apply an epoxy tie coat before two or three topcoats of regular bottom paint. I’ve found this lasts the best part of a season. Many don’t even worry about the tie coat, just slapping the bottom paint directly onto the bare metal, but I think it sticks better with a tie coat. If galvanic corrosion is a concern, try one of the copper-free products like Trilux or Velox Plus, a new paint developed specifically for running gear and outdrives.

Other products: Many have had success with zinc-based coatings like Pettit’s spray-on Prop Coat Barnacle Barrier, or even hardware-store cold galvanizing sprays. McLube’s Antifoul Alternative Speed Polish kept my propeller clean for 10 weeks but then wore off, resulting in the spectacular barnacle collection seen on the opening page. Probably the best of the alternative products—and certainly the most expensive—is Propspeed, a silicon-based compound that requires meticulous care in application but will last two or three seasons if properly done. I found this the most effective product I’ve used so far. Another thing I’ve learned—read the maker’s instructions, and follow them to the letter. If you take short cuts with any of these products, they won’t work as advertised.

Good old bottom paint is also effective on props

Good old bottom paint is also effective on props

Then there’s the ultimate solution—a black plastic bag pulled over your prop and held shut with a rubber band. If you have to leave your boat for an extended period, this is a fine way to keep the propeller barnacle-free—just don’t forget to remove the bag before you motor off on your return. To get around this embarrassing possibility, one enterprising chap has come up with the PropPak, a reusable plastic bag that can be removed from the cockpit.
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Finally, don’t neglect your propshaft. Coat that too, but leave the metal under the shaft anodes bare, and—I can’t believe I’m writing this—do not paint over your zincs. One tip I saw online somewhere sounded interesting—wrap a couple of layers of masking tape around the propshaft, then apply a couple of coats of bottom paint over the tape. At haulout time, just slit the tape with a razor blade and peel it off to expose a shiny shaft that needs no cleaning. Another old wives’ tale? It wouldn’t be the first…

RESOURCES

Barnacle Barrier

Pettit Paint pettitpaint.com

LanoCote

Forespar forespar.com

Propspeed

Propspeed propspeedusa.com

Trilux

Interlux yachtpaint.com

Velox Plus

PYI Inc antifoulingpaint.net

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