Prop anti-fouling treatments-is it worth it?

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..and sacrificial zincs get covered with marine growth as fast as any other underwater part that does not have anti-fouling on it.
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If they do then the zincs are not working. The tiny amount of current in them will keep them free of growth. In fact, this is one way to tell if a zinc anode is doing its job or not. I learned this from our marine electrical shop and the dive shop that does our boat twice a year.

This has always been the case on our boat and the boats I see come out on the Travelift in the yard in our marina. Regardless of the barnacle and weed buildup on the hull itself, the zincs or what's left of them are always totally growth-free.

A couple of times we have gone longer than we wanted between haulouts and bottom paint. The boat had a good coating of slime and "moss" below the waterline and a fringe of fine weed at the waterline even though we were using the boat regularly. When we got in the dinghy we could see the rudders had barnacles on their trailing edges. But the zincs on our transom were clean as a whistle in terms of growth and when the boat finally came out, so were the shaft zincs. They were deteriorating, of course, as they should. But nothing could grow on them because of the current, as miniscule as it is.

When the boat's in its slip we also hang a zinc about eight feet down off the stern on a heavy cable that's clamped into the boat's bonding system. The cable and the line the zinc's hanging on get thick with algae and weed, particularly in the summer. But the zinc itself will have nothing whatsoever growing on it.

So if you've got weed or growth on a zinc anode itself, that anode is not properly tied into the boat's bonding system. Could be a corroded connection-- -it doesn't take much to stop the tiny bit of current as I discovered the other year--- could be a broken connection, or something else. But if you've got bottom growth forming on a zinc anode, you've got a problem.

A couple of years ago when the dive shop changed our two transom zincs one of them started to deteriorate as normal but the other one stayed looking brand new. Then algae and weed began to form on it. That's when I learned what I related above. I checked the continuity of the bonding straps and wires in the lazarette and the continuity was good to the mounting bolts for both zincs. So why was one going away and the other wasn't?

I mentioned this to a good friend who is a retired marine engineer and he told me how little resistance it takes to stop the flow of current to an anode. On his suggestion I got some bronze wool and from the lowered dingy removed the non-working zinc from its mounting bolts under the swimstep. I polished the bronze mounting bolts with the bronze wool and reinstalled the zinc. End of problem. There was just enough surface corrosion or whatever on the bolts to isolate the zinc from the bonding system.

I usually replace the transom zincs myself because they are easy to reach and cleaning off the mounting bolts has become part of the routine now. And the problem of a non-deteriorating, weed-growing zinc has never come back.
 
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My zincs slowly dissolve so I assume are doing what they are supposed to do, but they always have a bit of algae on them when the boat comes out.
It would appear the main reason for going for PropSpeed in it looks like you can get up to 3 yrs out of it, and a similar time from good anti foul. So when you look at it that way, the extra cost over this magic zing stuff is justified. I don't want to have to haul out every year, or pay a diver to clean down several times a year, either. In fact I don't think we are allowed to do that in the water here anyway.
 
Interesting point about the anodes not getting a growth built-up if they are properly bonded.

Like Peter, my anodes do get some growth on them, however they do seem to be bonded as at about 18 months there is not much left. Will check the bonding system though. Other than a visual inspection can anyone recommend a good way to check if the boats bonding system is doing its job?
 
That would easily be 3 times as long as I've ever seen it last.

Well, I'll let you know soon, as she will becoming out after nearly 3 yrs in a couple of months, and I'll take pics.
 
I'll agree Marin..good tip..I'll be watching mine closer from now on.

Scary how many out there aren't working when boats are finally hauled...especially on outboards/outdrives that really need them.
 
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Just make sure you don't put any of your copper anti foul on the prop....copper will eat pinholes in that. Use a copper free antifoul like Smart Solution Outdrive Paint. Another factor to keep in mind...if you have a color bottom paint (like blue) then paint the prop with copper free blue it won't match. Copper based paint isn't as bright as the copper free stuff so stick with black for the prop.
 
It's like a battery reaction between the metals. That's why copper based paint isn't used on aluminum boats.

Yes, I understand that. What I didn't understand was that we had somehow ended up discussing outboard motor propellers.
 
Welcome Aboard!

If you use antifouling,it should be a hard type, not an ablative soft type you might use on the hull.
The best treatment for the running gear is Propspeed which I will do next time.
I am surprised the yard would ask that question.Maybe it was about using Propspeed.
How long a/f lasts depends on location. You`d hope the hull and running gear last as long as each other.

As someone suggested using hard vs. ablative...the hard will have copper usually so an ablative needs to be used. As a lot of ablatives will be marketed as outdrive paint, bottom paint, aluminum bottoms, props....
 
As someone suggested using hard vs. ablative...the hard will have copper usually so an ablative needs to be used. As a lot of ablatives will be marketed as outdrive paint, bottom paint, aluminum bottoms, props....

Most hard and ablative anti fouling paints that you would put on your hull are typically copper-based. If you are looking for an anti fouling product for an aluminium prop (and I still don't understand how we even got on the subject of aluminum props) you need to use a product that is zinc-based (tin being banned in most seafaring nations.)

Interlux sells an aeresol can of Trilux 33 and West Marine also sells an aeresol can of zinc-based paint for aluminum, simply called "Outdrive Spray."
 
Oh please don't start this again. It's been proven that the black pen trick is fake.

Oh really, I didn't know that. I'll stop using it right away.
 
Just to be clear on this, most of us have bronze propellers and it is safe to put a copper containing paint on them.
In my opinion no regular bottom paint, hard or ablative, lasts as long on a propeller as Prop Speed. I think it's worth the additional expense, others won't.

I think this is the zinc product that has been mentioned. I haven't tried it and don't know anyone who has so I can't express an opinion on it.
ZincCoatBarnacleBarriertn.jpg
 
Many Thanks to all. I never thought I would get so many replies from near and far. I am bringing the vessel up to the lower Chesapeake in April & will post more info and pics then. I will ask the marina in North Carolina what brand of treatment he plans to use-he did not specify in his quote. Thanks Again.

Where in NC? Which marina?

BTW I have PropSpeed here in NC and it works great. We have a diver all year round. He does every other month in the warm weather and every third in the colder months. We are going on three years and the bottom is getting thin. The diver tells me the he doesn't have to scrape anything from the prop or shaft. If something is on there he said it comes off with just a touch. He recommends that I just run the boat in gear at the dock every couple of weeks and that will throw anything that is on the running gear off.

We are hauling in April and we will be putting PS back on.
 
I too use Petit's Barnacle Barrier. After six months all of my underwater metal looks like the day I painted it. This year we will be staying in all year so I will put on an extra coat. At $25/can it is cheap, easy, and it works.

Dave
 
As someone suggested using hard vs. ablative...the hard will have copper usually so an ablative needs to be used. As a lot of ablatives will be marketed as outdrive paint, bottom paint, aluminum bottoms, props....
Antifouling running gear usually requires full prep, back to bare metal and priming, before a/f goes on. Would that insulate any metal dissimilarity?
BTW I understand Propspeed also requires back to clean metal prep.
I find a final clean with a wire brush mounted on a 100mm/4" angle grinder does the job.
 
I find a final clean with a wire brush mounted on a 100mm/4" angle grinder does the job.

Our yard recommended Scotch Brite pads on an air 90. It worked like a charm and went surprisingly quickly.
 
BruceK, you can put copper bottom paint directly on bronze running gear without primer and not have electrolisis. The primer is suggested to help the paint adhere to the metal. Don't forget that bronze is mostly copper.

"As someone suggested using hard vs. ablative...the hard will have copper usually so an ablative needs to be used."
Actually most ablative paints are copper based. The copper is only a problem on aluminum boats or aluminum props such as you might find on an outboard.
 
Zingard from Mgduff

It seams like there is no clear winner in this propeller coat competition - there is a lot of good stuff, some works perfectly well in one harbor but doesn't work 50 miles away. I guess there are too many variables, such as salinity, water temperature, propeller in direct sun or shaded, local currents, tidal influence, propeller speed (RPM), boat speed, how often the boat is used and the moon position :ermm:

So the best solution for me is one with compromises.

Mgduff Zingard (probably similar to Pettit) is a zinc product, which requires a little effort initially (but no more than other products).

The beauty of this product is that the next application - say two years later - only requires a quick washdown / cleaning of the propeller and then the next layer of Zingard can be sprayed on. No priming or other "demanding" jobs are required. The next layer of the Zingard is sprayed directly onto the old layer and bonds with it.

Once or twice during the season I plan on diving and then plaster the propeller with propeller grease to support the zinc.

The added benefit of Zingard (or other zinc products) is that it also acts like a zinc directly on the propeller and therefore protects against corrosion :Thanx:

PropeSpeed or similar products does not do this.
 
Like Peter, my anodes do get some growth on them, however they do seem to be bonded as at about 18 months there is not much left.

If your anodes are going away then they are doing their job. Perhaps the slight growth you and Peter see on them is due to your environment of warmer water and more sunlight. Where here in the PNW the cold water and reduced sunlight are enough to keep the anodes growth-free.
 
Well if zinc is so good why not take the prop to a galvanizer and have it hot dipped in zinc?

With so much surface area in zinc it could create an over zinced condition. And electrolysis could eat away the zinc faster than anti-fouling paint would fail.

ArmorAll seemed to work in Alaska for me and I know of nobody using it down here so I'll probably just stick w it until it fails it's so cheap and easy.
 
Good point, why are props not dipped in zinc? Weight or balance problems?

Mine is a CPP type and I don't think that hot dipping will work ..
 
I'm between coats now w the Petit Barnacle Barrier. The only thing that implies that it has any anti-fouling properties is in the name Barnacle Barrier. Nowhere else on the can does it suggest it has anti-fouling properties. But zinc is used in some anti-fouling coatings ... for fresh water I think. Got two coats on one side of the prop now. I plan on hauling next year and if the prop looks good I'll re coat w the BB. But that's next year.
 

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Should we assume your Armorall finally failed you, and that's why you switched to Pettit?
 
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Regular galvanizing (essentially Petit Barnacle Barrier) doesn't do much here in Jersey near an inlet...my bottom is still clean but rudder and prop are pretty heavily covered in growth. The bottom and running gear was painted in June with no movement since....maybe a low rpm turn of the engine back in July.
 
I'm ever the optimist Scott and Nsail I just don't think the Armor All will be effective down here in these long hot summers. But it hasn't failed. The Barnacle Barrier should be better and it's cheap and easy. Not as easy to apply as the AA though. I wonder how many don't put anything on their props. Perhaps most??
 
I wonder how many don't put anything on their props. Perhaps most??

Based on my twenty years hull cleaning experience, I'd say over 90% of boat owners do not coat their running gear.
 
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