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Discussion Starter #1
These weird and hard to clean spots have formed on my deck. They form in random patches. Please see these photos:






It's really hard to get them off - lots of scrubbing that I'm sure damages what's left of my non-existent gelcoat.

Does anyone have any idea what causes this? What I can do to prevent them? Also, any good ideas on how to clean it other than scrubbing and FSR?

Thanks!
 

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It's mold/mildew happens all the time seems like where ever boats are in the east. Power wash usually gets it off. hand scrub with "softscrub" works. tile cleaner works. white wall tire cleaner works too. but caustic. Seal and buff with "Woody Wax" I think is the most recommended.
 

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Mold!?!? Really! How the heck does that grow on the outside of a boat? I thought mold/mildew like cool damp places. The topside gets all kinds of UV and heat which I thought fungus didn't like.

I believe you, but wow - I just never would've figured. Thank you very much for the guidance!
 

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Discussion Starter #6
I just used starbrite deck cleaner for this very issue.
Spray full strength, scrub with a deck brush, after 3 minutres of so just hose it off.

Simple like that
I used that today - it helped but didn't take care of all of it. Since this was my first attempt to clean it - maybe I just need to reapply.

Now that I know what it is, I think I'll have an easier time figuring out what to use.
 

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Mold!?!? Really! How the heck does that grow on the outside of a boat? I thought mold/mildew like cool damp places. The topside gets all kinds of UV and heat which I thought fungus didn't like.

I believe you, but wow - I just never would've figured. Thank you very much for the guidance!
Denise is right....mold.

Right now, get in your car and find the nearest "Dollar Store". They're practically on every street corner here in Florida.

Go to their spray cleaner section and buy a couple of bottles of "AWESUM CLEANER". Yep. yellow liquid. This will set you back all of 99 cents a bottle.

Spray on the mold, let sit a minute and wipe off. EZPZ. This stuff is highly concentrated citric acid. Totally biodegradeable. I've been using it on gelcoat for years. Warning, if you let it sit on painted areas, it will remove the paint.

This stuff was made to clean gelcoat... just sayin..
 

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These weird and hard to clean spots have formed on my deck. They form in random patches. Please see these photos:






It's really hard to get them off - lots of scrubbing that I'm sure damages what's left of my non-existent gelcoat.

Does anyone have any idea what causes this? What I can do to prevent them? Also, any good ideas on how to clean it other than scrubbing and FSR?

Thanks!
It's called "Pinpoint Mold" and is growing in the pores in the GelCoat which is evidently very worn and has lost its glaze. Try covering it with paper towels soaked in chlorine from a pool company--not household bleach. The stuff will destroy the paper towel material quickly but should also destroy the mold if left over night.. Dose with a bit of Wink rust stain remover and then wash the area thoroughly with warm soapy water and rinse with fresh and then compound and polish. You've got to kill the mold spores and fill the Gelcoat pores. BTDT...
 

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Discussion Starter #9
I'll try the dollar store citrus cleaner first (thanks TropicCat), if that doesn't work I'll look for the stronger stuff that svHyLyte recommended.
 

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Denise is right....mold.

Right now, get in your car and find the nearest "Dollar Store". They're practically on every street corner here in Florida.

Go to their spray cleaner section and buy a couple of bottles of "AWESUM CLEANER". Yep. yellow liquid. This will set you back all of 99 cents a bottle.

Spray on the mold, let sit a minute and wipe off. EZPZ. This stuff is highly concentrated citric acid. Totally biodegradeable. I've been using it on gelcoat for years. Warning, if you let it sit on painted areas, it will remove the paint.

This stuff was made to clean gelcoat... just sayin..
I am going to try this for fine tuning my cockpit...Thanks
 

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Part two of your question was how to make it stay away.

Fill the micro pores/holes with wax, buff etc.

The only other way is to sell the boat and take up extreme rocking chair sports.
 

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I had the same problem...only worse. It was all over my topsides.

Here is a shot of the cockpit. Almost all of the black on the transom was the mold.

I used diluted bleach and a Scotch Brite pad, followed by large amounts of water.

 

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I had the same problem...only worse. It was all over my topsides.

Here is a shot of the cockpit. Almost all of the black on the transom was the mold.

I used diluted bleach and a Scotch Brite pad, followed by large amounts of water.

Do we get an 'AFTER' picture??;)
 

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FSR cleaner would make that white again, but then you'd need to compound and wax it.
 

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I'll try the dollar store citrus cleaner first (thanks TropicCat), if that doesn't work I'll look for the stronger stuff that svHyLyte recommended.
We did not find that the Citrus cleaners worked very well and finally went with the more aggressive method mentioned. If the Citrus oil approach works for you, it is important to ensure that all of the residual oil is thoroughly removed as we discovered the stuff becomes medium for mold itself once its acidic content is depleted. Note that if you are in an area with a fair amount of air pollution, the finish surface on Gelcoat and/or wax will erode fairly quickly as moisture in the air combines with the sulfur in the air particulates to create acid (think acid rain). Frequent washing and wax application is the only defense.

In any case, Good luck...
 

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FSR cleaner would make that white again, but then you'd need to compound and wax it.
I tried FSR and it was unable to remove the black spots. I will be compounding and waxing before launching again to protect all my hard work :)
 
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