Need to be alarm? Barnacles and corroded zinc after 6 months?

[SeacretSailor]

Guys,
As a new sailor, I keep my new '78 C&C 29 here in Lake Pontchartrain in Mandeville, north of New Orleans. My marina is 3/4 mile up the bayou, so the water is a warm and brackish/fresh mix. When I bought her, I had it hauled and bottom painted with Pettit Trinidad. Today, I went sailing and wanted to check out the bottom with my mask/fins.

I found the shaft zinc 50% corroded, lots of slime on the hull and barnacles on the prop. I scraped the prop clean easily and the slim came off with just my hand rubbing it. Glad I checked the shaft zinc! I'll have to go overboard next weekend and replace it.

The barnacles surprised me, but I can scrape it every 4-6 months.
The corroded zinc surprised me, guess I'll replace it every 6 months.
After using the most expensive AF paint (what everybody recommended in the area) the slime surprised me? It did come off easy with just a stroke of my hand, BUT who wants to get in the water every 4 months and do underwater hull maintenance? Us southern Louisiana sailors don't haul in the fall like the NE sailors, I plan to haul every 3-4 years and it'll stay in the water year long.

Any thoughts? Do I need to look at buying one of those zinc "Guppy" things or look at stray current on my boat or my neighbors?

Sometimes trailor sailing was so much simpler.....

Kevin B.

 

[CalebD]

What you describe does not in the least surprise me.
We keep our sailboat on the Hudson River on a mooring in brackish water that is obviously cooler then the water of Lake Pontchartraine most of the time. We get similar results to what you are describing except that sometimes we are able to use the same shaft zinc for 2 or more years before replacing. I am sure that temperature has something to do with it is well.
I am going out on a limb speculating that you keep your boat in a marina at a slip and because of that the stray electrical current from other boats, in close proximity, may be helping to eat away your shaft zinc.
Slime and barnacles happen in brackish water. This year we had a very wet June with lots of rain and although the barnacle growth was somewhat inhibited (smaller growths then usual) we had plenty of slime the last time we cleaned our hull (3 weeks ago we hauled out for a prop and hull cleaning before our final winter haul out).
It sounds to me as though you used a decent paint although maybe you did not add enough Tabasco sauce to it! Just kidding - I don't have any reason to believe that Cayenne pepper or Tabasco would help.

Bumper sticker recently seen: "If a dirty bottom slows you down, think about what it does to your boat!" (Tommays)

My best.

 

[Guest]

Paint

Hi Kevin, seems normal to me, at least what I experience here in the PNW. The paint brand you used, is it ablative or hard? When we purchased our boat in 2002 I installed three coats of WM brand ablative paint. Then did it again in 2004. Each year since I have a diver check the bottom, install fresh zincs and scrape any barnacles off of the prop and shaft (usually one or two).

If the brand you use is ablative try to avoid rubbing marine growth off its surface. That tends to destroy the benefits of the paint. I cruise year around and after a few weeks the hull will collect a growth of marine life. Once I head out that marine growth sloughs leaving a thin fuzz.

Depending upon your location zincs can last from six months to a year. Actually, losing 50% of your zinc in six months is pretty normal. What can also help is to connect a wire to your boat ground on one end and to a large flat zinc on the other, then drop the zinc with the connected wire into the water. It will tend to absorb some of the galvanic electricity in the water and help extend the life of your boat zinc.

Desitin (used on baby bottoms) contains zinc oxide. The next time you dive, slather on some to any bright work. It will help keep marine life from growing on your prop and shaft. I've tried it and it works.

Terry Cox

 

[Paul Mermelstein]

This is all normal. I use the same paint you did and I am in brackish water off the Chesapeake Bay. I have a diver clean the bottom and check the zinc 2-3 times per year. He reports the same thing: just some barnacles on the prop and some slime on the hull. He cleans it off and voila. My zinc is replaced annually.

I don't think cleaning the hull and prop every few months is unreasonable.

 

[Joe]

That's normal. Bottom paint doesn't prevent the growth completely, but it slows it down considerably. Hire a dive service to clean the bottom and check the zincs once a month. Just another cost of boat ownership.

 

[Hermit Scott]

Kevin-I am in Corpus Christi. I have to scrape barnacles off my prop every month.
The slime build up tells us that you aren't sailing enough. If you sail more it will keep that off. The slime comes off easy enough. Don't scrape your hull!!!!! Your paint will come off with anything you scrape off. A sponge is the coarsest thing you should use on the bottom paint. But sailing is the best way to keep the green slime off. Some people use a pressure washer, I would not do that. Pressure washers can etch wood, that can not be good for a soft ablative paint.

 

[alexco38]

That's why newer production boat has Galvanic Isolator. It installs between the ground wire on your boat to the shore power cord. It induced 1.4V voltage difference thus prevents galvanic action. Just google it or you can make one yourself. Just connect two diodes in series forward and two diodes in series backwards. Each diode drops about 0.7 volts. Forward and backward is for AC. Make sure the diodes are rated higher current that your demand and higher voltage than 380v for spikes. Put them on a heatsink and you won't loose zinc as fast.

 

[JoelHoover]

It's customary out here in California to have divers clean your boat every month. There's also some large, u-shaped foam brushes that allow you to clean the bottom while your standing on the dock.

I love St.Tammany Parish. Years ago I used to rent a small apartment in Madisonville right on the Tchefuncte river. Bon Temps!

Nice C&C you got there, Coonass