Propellor Paints Versus Barnacles

Posted by Darrell Nicholson at 12:01PM - Comments: (14)

Mahina Expeditions,
Mahina Expeditions,

Severe fouling is particular troublesome on folding props like the MaxProp (shown above), as well as feathering props, like the Gori. Practical Sailor compared folding and feathering props in the February 2018 issue online.

A cheap, effective antifouling paint for a propeller is as rare as a good pun. The coating must not only ward off all marine growth, it must present a smooth slick surface that can stand up to the constant water friction when the boat is under power. And in the case of a folding prop, the coating must also adhere in nooks and crannies and, in some cases, even withstand metal-to-metal contact. These demands are well beyond the reach of any run-of-the-mill marine coating. Thus, we embarked on our search for—wait for it—a prop(er) paint.

Yes, you can paint a bronze propeller with conventional, copper-based hull paint, but it won’t do much good, since the more noble metals in the bronze prop will eventually waste away the copper biocide. Don’t even think about painting an aluminum outdrives or prop with a copper paint, or the reverse will occur—the more noble copper will attack the outdrive alloys. Even with the right preparation, regular bottom paint tends to wear quickly on a prop due to increased water friction.

by Frank Lanier
by Frank Lanier

Props and struts are particularly difficult to protect. Sacrificial shaft anodes, whether zinc or aluminum, should not be painted. We compared aluminum and zinc anodes in the January 2017 issue online.

Practical Sailor’s search for longer lasting prop paints has led us down many rabbit holes, we've experimented with several different prop paints with varying degrees of success, although none of the results so far have been dazzling. Some of our testers have had better success with dedicated “slick” prop paints such as PropSpeed. In our testing, however, mostly in Chesapeake Bay, no prop paint had lived up to our increasingly faint hope that the paint repel growth as effectively as our hull paint.

For previous articles on this topic check out our report on the dedicated propeller paint PropSpeed (see PS February 2014 online), and a more detailed report on prop paints in general (see PS July 2010 online).

We also looked at Mussel Buster (see PS October 2011 online), a baked-on powder coating that, like PropSpeed, relies on its slick, hard coating (as opposed to biocide) to prevent barnacles from adhering. Other products our testers tried include Feldtens Nano propeller spray treatment, an inexpensive product that appeared no more effective than others. Like other prop paints we have tested, both the Prop One (formerly Prop Gold) and Velux Plus showed signs of failure after less than six months of use. The Velox Plus (primed, left, and painted, middle) began to flake off the prop (right), but it was still fighting barnacles.

Lately, we have advised sailors to take one of two options:

Jonathan Neeves
Jonathan Neeves

We compared two slick coatings, Velox (left) and Prop One (formerly Prop Gold) in the March 2017 issue.

Option 1: Blast the prop to bare metal, prime with Interlux Interprotect or a similar barrier-coat epoxy, and then paint with a conventional hard bottom paint. (Although the epoxy theoretically prevents galvanic reaction between dissimilar metals, copper-based paints are to be avoided.) The trick with using a conventional bottom paint (sprays like Interlux Trilux 33 or Pettit Alumaspray are easier to apply) is getting it to adhere, thus the epoxy primer. Although there are options other than epoxy for priming a prop, because of health concerns, these etching primers are not considered do-it-yourself friendly (although they were used that way for years).

Option 2: Use Pettit Barnacle Barrier, a spray zinc product that has given us a year’s worth of protection in the Chesapeake. Because the prime-and-paint routine hasn’t delivered dividends commensurate with our effort, we’ve found that applying multiple coats of the relatively inexpensive Pettit Barnacle Barrier is the most practical option for boats that haul out annually. (Readers have also reported unsatisfactory performance with Barnacle Barrier.)

Option 3: Take your pick of the dedicated "slick" prop coatings we've tested. Results will vary (as our tests have shown) but all should provide longer lasting protection than either of the above options if they are applied as directed. However, the added cost might not be worth it to the boater who hauls and paints each year. 

If you'd had good (or bad) results with any of these options--or something else--we'd like to hear about your experience. Be sure to include the boat's type, name, home port, and location and pattern of use during the period the paint was in use (i.e. sailed weekly, daily, monthly in San Francisco Bay. . . ). You can respond by email at  Comments are also appreciated. 

Comments (14)

Agree with Roland. I've been using the Rustoleum Cold Galvanizing Compound here on Long Island for a few years now with very good results. I can get it at my local Lowe's for under $10 a can, which is more than enough to prep for a season.

Posted by: Capt. Kevin | December 18, 2018 9:35 AM    Report this comment

My sailboat lives in the Southern Chesapeake Bay. After trying a number of prop treatments, I've settled on Rustoleum Zinc-rich Cold Galvanizing spray paint, 2-3 coats on a clean prop. Not perfect, but will protect through a complete season with minimal barnacle growth (no soft growth). Desitin sorta worked, but quickly wore off the leading edges, which rapidly grew a line of barnacles, fouling the prop. A large tube cost as much as a can of the Rustoleum (about $12). My sailing buddies using yard-applied Prop-Speed and other fancy coatings all had more problems with fouling than I, at far greater expense.

Posted by: Roland52 | December 14, 2018 7:47 AM    Report this comment

I have a saildrive and use Velox on that, which seems to do a decent job. I tried to paint the prop with Velox, per the directions, and was disappointed. I have had better results on the folding prop using green grease. A thin coat, brushed on, lasts about 3 months and can be re applied in the water. A

Posted by: RichardGr | December 13, 2018 8:42 PM    Report this comment

So what specific " Rustoleum brand for 1/3 of the price and works just as well" is it. Please don't play I've got a secret.

Posted by: Squattybligh | December 13, 2018 5:22 PM    Report this comment

I seem to remember that a number of years ago Desitin (for baby bottom rash) was given by PS or some other publication as a solution to marine growth on props and shafts. As I remember I tried it and it seemed to work well. Can any one confirm that I am not delusional ?

Posted by: CR | December 13, 2018 3:14 PM    Report this comment

The same formula as barnacle buster can be purchased in a hardware store under the Rustoleum brand for 1/3 of the price and works just as well.

Posted by: Dennis B | December 13, 2018 11:50 AM    Report this comment

The same formula as barnacle buster can be purchased in a hardware store under the Rustoleum brand for 1/3 of the price and works just as well.

Posted by: Dennis B | December 13, 2018 11:50 AM    Report this comment

The same formula as barnacle buster can be purchased in a hardware store under the Rustoleum brand for 1/3 of the price and works just as well.

Posted by: Dennis B | December 13, 2018 11:50 AM    Report this comment

I have my boat (ARIA, Catalina 36) in the Housatonic river in Stratford Connecticut. I've been using Pettit Barnacle Barrier for several years with satisfactory results We are in 6 months each year, and the water is brackish and constantly moving (Housatonic river estuary). There will be a few barnacles on the prop and shaft but nothing like what the folks who don't use anything experience. I put 3 coats on and it seems to work fairly well

Posted by: gerryfs | December 13, 2018 11:30 AM    Report this comment

I'm on a mooring in a Florida barnacle factory and this has been a constant problem. I'm a little better off now: I have a Kiwi feathering prop which has composite blades and stainless guts; this can be painted with bottom paint (ABC3 lately). I also have an ultrasonic system onboard running 24/7, 3 amps continuous, about like leaving your refrigerator on. Solar panels do keep up with it though. Bottom line: paint lasts about a year, I go two to three years between haulouts. The ultrasonic does a pretty good job in combination with bottom paint; as the paint wears the ultrasonic cannot do it all. The ultrasonic has a much more limited effect on appendages than the hull itself. You would need a puck on the rudder and running gear and that would be an additional power load on the system, as well as an up front cost, that I am not currently willing to accept. Now I do bi-monthly bottom cleanings and spend the same amount of time on the prop as the whole rest of the hull, keel and rudder (34' LOA). It is better; in the past after a month my prop could look like a volley ball.

Posted by: DanoMielke | December 13, 2018 11:17 AM    Report this comment

Wouldn't the propellor be the perfect place to try the ultrasonic barnacle prevention technology? A small area of hard material seems like the ideal candidate for such an approach. Has anybody tried this? Fran De Faymoreau. San Francisco Bay area

Posted by: Fafoupanou | December 13, 2018 10:27 AM    Report this comment

I have good success, no hard or soft growth on prop or shaft, using Pettit Barnacle Barrier, usually 3 coats, as a primer then. I cover it with Pettit Hydrocoat SR, two coats which is also used on the hull. My boat, Jambaby - Sail, is in the water from early May to late October and used almost every week and is moored in Mamaroneck, NY (Long Island Sound).

Posted by: Jambaby | December 13, 2018 10:15 AM    Report this comment

In Baja (six months wet, six months on the hard), a good thick coat of hardware store spray galvanizing worked great. Almost as good was a smearing of Desitin (lanolin and zinc oxide). Propspeed gave us two years...totally not worth it.

The best "fix" is to stay out of LaPaz. The river is a barnacle factory. We stayed there anyway. It's lovely.

Posted by: Capt. Phil | December 13, 2018 10:12 AM    Report this comment

I've been satisfied with using the regular ablative bottom paint on my prop & shaft that I use on my hull, but my boat is stored on the hard most winters and it moves around a lot in the summer. It's been in Washington and British Columbia for several years and is now in SE Alaska stored in a yard. Since it's out of the water half of the time, the growth window is too small for much buildup, and what little does build up is easily removed. The downside is that I have no permanent marina home; the advantage is that the bottom paint is easily refreshed. Not going to be much help if you prefer to avoid hauling nearly every year...

Posted by: Dan Morehouse | December 13, 2018 9:49 AM    Report this comment

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