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I never see painted shafts, so I don't think you forgot to do anything. You should also have zinc collars on your shaft. Yeah - I get barnacles on my shaft also, I knock the big parts off with something hard like a scraper, and finish with scotch bright or a wire brush. They come off easier if you get them when they are wet, and don't let them dry out.
I've used Petttit Prop-Koat on my propeller with some success, but its very expensive and application is a two step process (primer and clear coat finish). I might be tempted to try it on my shaft but I would be careful to avoid coating where the zincs were going, you want a good electrical contact between the zinc and the shaft.
I never see painted shafts, so I don't think you forgot to do anything. You should also have zinc collars on your shaft.
I've used Petttit Prop-Koat on my propeller with some success, but its very expensive and application is a two step process (primer and clear coat finish). I might be tempted to try it on my shaft but I would be careful to avoid coating where the zincs were going, you want a good electrical contact between the zinc and the shaft.
I am not that ignorant I have zincs on my shaft and I wouldn't dream of putting anything between them and the shaft.
Someone in my boatyard said that he had sprayed his shaft with a product from WM [I do not recall the name] and it kept the marine growth off his shaft and prop. I will have to ask him what he used.
"Expensive" is a polite way of characterizing the Pettit-Koat. But I guess for $175 you get 10 yrs use out of a quart.
I must be missing something here. My aluminum rudder shaft was badly damaged by copper bottom paint. I know it because the only place eaten away is right at the bottom paint line, nothing above or below. However I fail to see how copper bottom paint could damage a copper alloy! I'd have to believe it was electrolytic action from stray currents, and no zincs.
May I ask why it makes a difference to not paint your prop; while most people paint their thru-hull, stanchion and skeg? These items had 30 years of paint on them on my boat; and none had the de-zincification that was shown in the pictures of the props over on that thread.
I don't discount the possibility that the paint causes galvanic corrosion; but I am wondering why it would be different for a prop than a thru-hull.
Well.... that makes me feel a little better. I tried that stuff for the first time this year and at a fall haul the prop and shaft had hundreds of barnacles. But..... in the N.E. it was a good year for barnacles with the wet June we had and I didn't get out that much. It's all I had so since it was just a short haul I cleaned and re-painted with the same..... we'll see next haul.
And.... another... But..... a couple guys who keep their boat in the same area saw my mess and boasted about the much better protection they got from the 2 part (actually 3 with primer) EP2000 at $67 a quart.
So much of it seems to be where and when.... I'm a bit deeper into the small cove and the few things I've read about barnacles makes me think it's more of a crap shoot than I would like to beleive
The zinc will dissolve IF it is not protected by another piece of pure zinc. This will happen regardless of if there is copper paint on it or not. If this is true; then again I ask why the same chemical reaction does not take place on non-grounded fittings like thru-hulls and skeg shoes?
more info on spray-on barnacle prevention for prop shafts
The product that I was told about is Pettit's Zinc Coat Barnacle Barrier.
Product description from one retailer's web site:
Pettit Zinc Coat Barnacle Barrier 1792 is specifically designed to be used on bare metals such as steel, stainless steel, cast iron, copper, bronze, galvanized steel and lead, both above or below the waterline. Zinc Coat forms an excellent adhesive bond to underwater metals and running gear and inhibits corrosion on these surfaces. Properly applied, Pettit Zinc Coat Barnacle Barrier yields a smooth, hard surface that self-cleans under way.
Price for a 16-oz spray can is about $22.
Edit: I just saw the previous post reporting negative results for this product. But the guy in my boatyard had a clean shaft at haul out and mine is a mess, and we were both in the same harbor all season.
Seems these things are subject to a lot of variables...I can only say that for me, the Pettit Zinc Coat Barnacle Barrier Spray works well. That means I found that it reduced the amount of barnacles to an acceptable amount (two dozen or less).
We use the boat often except August and dead of winter.
Kept on the Chesapeake Bay in brackish water in a shallow creek where summer water temps reach 80+
KeelHaulin
"Why the same chemical reaction does not take place on non-grounded fittings like thru-hulls and skeg shoes?"
I think specifically because they are not grounded (and I don't believe they should be). By not being grounded they are not a connected part of the "electrical mix" underwater, and at least as far as thru-hulls are usually a fair ways from the prop and shaft physically as well.
I received an interesting link in an email that is from a company selling a prop for the Atomic 4 that besides better performance promises to almost eliminate prop fouling (I have no association). Scroll down to "No More Barnacles!" Boat Seem Underpowered?
Makes for interesting reading.
Brian
I am not sure that anyone fully addressed the cleaning of your prop. I have had great success with fine emery(sp?) cloth (waterproof sandpaper) and straight vinegar.
Put the vinegar in a spray bottle. Spray the vinegar on and lightly sand. It takes some time, but the prop and shaft look like new.
I just had a 33 year old Pearson surveyed. The prop was painted and barnacle covered. The surveyor advised me that a prop should produce an audible "ring" when tapped lightly with a piece of metal. lack of a ring indicates dezincification which can result from copper paint on Bronze. His advice was not to paint the prop, but to polish it to a bright shine, which slows down growth. Here is a photo (from before I got religion) showing the prop on my former inboard powerboat, after refurbishing by Ocean Props in Middletown, RI.
Note: I since learned that the nuts are on backwards in this picture. The thin nut is supposed to go against the prop with the thicker nut on the end of the shaft. It ran like that for a couple of seasons after which I reversed them. Don't think it made any real difference.
ChuckA - you had the prop shaft nuts on CORRECTLY in your photo - the thick nut should be next to the prop - its numerous threads take up the axial load of "pushing" the prop onto the shaft taper - the thin nut is only a jam locking device to keep the whole mess from un-screwing (just in case anybody else looks at this thread!).
As far as prop anti-fouling goes, I watched a fellow sailor having his boat pulled after a long (early May to 25 October) season here in Buck's Harbor, Maine - not a barnacle on it! His secret - stove black! You know, the stuff that comes in a tube that you buff onto the surface of your wood stove to make it - well - black! I wouldn't have believed it if I didn't see it myself! Anybody else ever try that?? It will be on my prop next Spring for sure!
I'd point out that vinegar or acetic acid will remove the barnacle bits...without damaging the metal.
Polishing the surfaces makes it more difficult for the underwater growth to adhere...but coating it with something like vaseline or such will help prevent growth as well...
I'd point out that vinegar or acetic acid will remove the barnacle bits...without damaging the metal.
Polishing the surfaces makes it more difficult for the underwater growth to adhere...but coating it with something like vaseline or such will help prevent growth as well...
The Petit spray has been the best I've found. In the Chesapeake from
April till November and only cleaned once in August, in the water and scraped by hand. This was the second year I've used it and I found that several coats (3 or 4) gave better results than the two coats applied the previous year. Maybe 2009 was a milder year for barnicles in Rock Hall, but I don't think so. Anyhow, next spring I'll be applying six coats of Petit Zinc Spray.
ChuckA wrote> I since learned that the nuts are on backwards in this picture. The thin nut is supposed to go against the prop with the thicker nut on the end of the shaft. It ran like that for a couple of seasons after which I reversed them. Don't think it made any real difference.
BELLATRIX1965 wrote > ChuckA - you had the prop shaft nuts on CORRECTLY in your photo - the thick nut should be next to the prop - its numerous threads take up the axial load of "pushing" the prop onto the shaft taper - the thin nut is only a jam locking device to keep the whole mess from un-screwing (just in case anybody else looks at this thread!).
That's what I used to think too, but I've been told otherwise by people with more knowledge and experience than me. The image below is from the installation instructions on the Michigan Wheel website it clearly shows the thin nut going on the shaft first, followed by the thicker nut.
I'm not sure why. I think it has to do with most of the load is taken up in the first 1.5 threads. The flexibility (thinness) of the nut affects the load distribution as well.
I'm a lover, not a fighter, so I'll let it drop at that.
Cheers,
Chuck
The prop nut debate is interesting. A couple months ago I got a copy of Professional BoatBuilder and they had an extensive article on it. It seems there is an ABYC standard on it, and the thin nut goes against the prop! The reason makes sense. When you tighten the outer nut it it unloads the threads on the inner nut. So you want the outer nut thicker to carry the load, and the inner nut locks it by friction.
I am in the same creek as t37chef. Like him I use the petit spray and am amazed with the results. When swimming in the summer I put the snorkel on and do a few dives and use a green pad to take of any critters who want to nest..
Dave
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