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Catalina/Capri 25/250 Sailor's Forums

General Sailing Forum

Black Algae Spots: Removal?

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dave andersen
1st Mate

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85 Posts

Initially Posted - 07/21/2009 : 09:39:40

Our 1986 C-25 was bought in May. Since then we have tried without success to remove small black algae spots from the cabin top and the foredeck. A stiff bristle nylon brush, a tooth brush, a scottpad, bleach, none work. All that really works is a fingernail to get down in the textured nooks and crannies.

Is there a way to remove these blemishes without wearing one's fingernails down to the bone?

Edited by - on

GaryB
Master Marine Consultant

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USA
4304 Posts

Response Posted - 07/21/2009 : 09:41:15

Sell it and buy a boat without algae spots?

Try Mr. Clean Magic Erasers. You should be able to get at most any store. I'd go with the heavy duty version.

Edited by - GaryB on 07/21/2009 09:43:25

Ben
Master Marine Consultant

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USA
1234 Posts

Response Posted - 07/21/2009 : 10:01:44

I have had a lot of luck with Softscrub.

Edited by - on

NautiC25
Admiral

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USA
957 Posts

Response Posted - 07/21/2009 : 11:00:42

I wonder if there's just different kinds of black algae, cause the stuff I have comes off with a hard scrub from a medium bristled brush. Haven't had time to do a real cleaning.

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delliottg
Former Mainsheet C250 Tech Editor

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USA
4479 Posts

Response Posted - 07/21/2009 : 11:42:11

I've had stuff that wouldn't come off till I hit it with a pressure washer. However, I've had really good luck with Softscrub for almost everything else.

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Steve Blackburn
Master Marine Consultant

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Canada
1091 Posts

Response Posted - 07/21/2009 : 11:47:03

I've had great results with Easy-Off oven cleaner. Took care of the all kinds of spots including cooking stains. Looks brand new now.

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Nautiduck
Master Marine Consultant

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USA
3704 Posts

Response Posted - 07/21/2009 : 12:44:25

I use Starbrite deck cleaner with PTEF for all stains on our deck and it always does the job. I keep a small spray bottle of it for spot cleaning. I have also used white vinegar to remove stains. With either of these just pool some of the solution on the stain and let it sit for a while. Then come back and go at it with a brush if needed.

If none of the techniques described in the posts above work then it might be time to lightly sand the stains with a fine sandpaper. Folded, the edges can go in the non-skid surfaces.

Edited by - on

dlucier
Master Marine Consultant

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Virgin Islands (United Kingdom)
7583 Posts

Response Posted - 07/21/2009 : 13:12:37

I've found Black Streak Remover (Walmart $5.00) to be a pretty good all around cleaner. It works great on bird crap, tree sap, organic stains, and, of course, black streaks.

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Derek Crawford
Master Marine Consultant

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USA
3321 Posts

Response Posted - 07/21/2009 : 14:48:12

Dave - are you sure that it's not spider poop? It's tough to remove but I've had success with Chlorox Clean-Up with bleach.

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Stu Jackson C34
Admiral

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844 Posts

Response Posted - 07/21/2009 : 15:08:11

Try acetone, dampen an old towel rag which will provide a bit of friction, followed with boat soap. Anything like even soft scrub has compounding ingredients that leave small hard to see scratches that will pick up even more dirt. Follow with a light waxing.

Acetone is also great for getting rid of black marks on the hull.

Edited by - Stu Jackson C34 on 07/21/2009 15:09:11

danandlu
Navigator

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USA
175 Posts

Response Posted - 07/21/2009 : 15:42:25

Tilex has worked very well for me. My mold (black spots) may be different than yours.

Edited by - on

Oscar
Master Marine Consultant

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USA
2030 Posts

Response Posted - 07/21/2009 : 17:55:41

I know the stuff you're talking about....and I think it's not algae but a mold. Had it on my 42, maybe it's a Catalina thing? The only thing that got rid of it completely was 1000 miles of sun and salt. A month in dock and it is back. Wax seems to seal it in, and it grows underneath the wax. I know, not much help.

Try a biocide......seriously.

Edited by - on

dave andersen
1st Mate

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85 Posts

Response Posted - 07/22/2009 : 17:00:04

Many good suggestions here. thank you.

The spots are black, irregular, right down in the
nonskid. When I scratch at them with my fingernail,
the residue that is lifted turns green. They will come off
but only with persistent work, one at a time. I've tried a
stiff brush with Softscrub, West Marine fiberglass cleaner,
dawn dish soap -- nada. I have hundreds so one at a time
seems foolish-- I'd rather be sailing

Now I will begin to try the suggestions from my expert panel.

Edited by - on

Turk
Admiral

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USA
736 Posts

Response Posted - 07/22/2009 : 18:14:04

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by dave andersen
 Many good suggestions here. thank you.

The spots are black, irregular, right down in the
nonskid. When I scratch at them with my fingernail,
the residue that is lifted turns green. They will come off
but only with persistent work, one at a time. I've tried a
stiff brush with Softscrub, West Marine fiberglass cleaner,
dawn dish soap -- nada. I have hundreds so one at a time
seems foolish-- I'd rather be sailing

Now I will begin to try the suggestions from my expert panel.
<hr height="1" noshade id="quote"></blockquote id="quote">

Dave

One more possibly off the wall suggestion. Swimming pool owners for years have fought chemical stains on surfaces. I recently had a very stubborn and I now know, chemical stain caused by metal and mixtures of other chemicals. The solution to the problem was ascorbic acid or vitamin C. Start by crumbling a vitamin C tablet and rub it on the stain. If it works, you can buy powdered ascorbic acid from any chemical house. It cleaned my entire pool without rubbing. I almost could not believe it. The bulk powder is used to make the tablets.

Edited by - Turk on 07/22/2009 18:14:54

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