Stubborn Waterline Stains

[Catalina007]

also try using Barkeepers Friend. About $2.50 and does the job.
But ots all short term success.  The gelcoat surface becomes pourus when old and the only real permanent cure is a new paint job at the emd of the day 


   

[Ron Hill]

Guys : Barkeepers Friend has Ocylic (sp?) acid in the powders form.  FSR (Fiberglass Stain Remover) has the same acid in the gel form. 

I was much happier when I moved the water line up - because that small white strip was usually under water anyway (hence the stain).  That's why Gerry Douglas told me that the 3ft+ draft (wing keel) was a design goal which Catalina missed!!  The real draft (C34 loaded) is closer to 4ft 5 in.  So you might as well raise the water line anyway because the boat sits lower in the water than the gelcoat trim was designed for!!!  Save yourself some work each spring!!

A few thoughts

[Jim Hardesty]

The gelcoat surface becomes pourus when old and the only real permanent cure is a new paint job at the emd of the day

My thoughts exactly.  I think if you don't have 2-3 inches of bottom paint above the static water line, consider moving it up. Think painting the white would work.  Really, IMHO, the only ones that get a close look at the hull below the boot stripe are fish and seagulls.  Not the usual sort that I try to impress with a bright white stripe.  Lots of other things much higher on my priority, much to the chagrin of the fish and seagulls. 
Sorry if I sound dismissive but really it's only obvious when the boat's out of the water.
Jim

[Roc]

Although this says rust stain remover and waterline stain is not rust, it does wonders for waterline stain.  Was with a friend who was cleaning up his Marshall Catboat and he pulled out this stuff, sprayed it on a sponge, wiped it on and the waterline stain came completely out!  He then sprayed the residual off and the hull looked brand new.

https://www.westmarine.com/star-brite-rust-stain-remover-22-oz.-126823.html

[Ron Hill]

Guys : FSR has NEVER let me down on removing stains.  Another cleaner (I'm told) are the Magic Pads, although I've never tried one!!

A thought

[Jeff Kaplan]

As I used to rep CRC chemicals, their marine division is Mary Kate.  I have always used their On-Off, yes it is dangerous but it does a great job.  Pour it into a plastic pail, use a cheap chip brush with natural bristles,3 or 4", wear gloves and hold pail away from you,  the results are amazing.  I have been using this product for years with no problems.  However, Ron, I might raise the water line.

[KWKloeber]

yes it is dangerous but

What's it base that's dangerous?

[Jeff Kaplan]

KW,  maybe the word dangerous should not have been used. There is an acid base in the mix, dangerous if not handled properly meaning you could get an acid burn if you don't wear rubber gloves or if a drop or 2 gets splashed on you.  Also the fumes are not really nice, I hold bucket at arms length. However, it removes the growth at the waterline and the yellow look above the water line.  Used correctly, it does the job.  This product will not harm the gelcoat

[Jeff Kaplan]

Another note, if using this product, use rubber gloves that are designed for chemical use, not cheap disposable gloves

[Ron Hill]

Jeff : I got tired of that thin white stripe and keeping it clean so I moved the water line up almost 3 inches and covered that white stripe with bottom paint.  Much easier to maintain and I couldn't see that stripe when I was in the cockpit anyway!!!   

A thought

[Jeff Kaplan]

Instead of painting the white stripe, I have been using white boot stripe tape , but that gets all munged  up at the water line as the paint does.  Ron, I think your solution to eliminating the stripe and painting over with anti-fowling will solve this problem, as said, once on the boat, stripe can't be seen. Gonna be a long winter, happy holidays to all...Jeff

[KWKloeber]

KW,  maybe the word dangerous should not have been used. There is an acid base in the mix, dangerous if not handled properly meaning you could get an acid burn if you don't wear rubber gloves or if a drop or 2 gets splashed on you.  Also the fumes are not really nice, I hold bucket at arms length. However, it removes the growth at the waterline and the yellow look above the water line.  Used correctly, it does the job.  This product will not harm the gelcoat

No, dangerous is appropriate any time DIY-ers are dealing with acids or strong bases.  What i was wonder is what's the constituents- i looked it up and on-off is basically like 15% HCl.  That's like half strength muriatic acid which is probably a lot le$$ at a big box.  The stuff I buy for work is typically about 30% HCl and around 5 bucks.  There is oxalic in there (which IIRC is the active ingredient in FAR.  IF oxalic (wood bleach) works on the stains that's probably also le$$ at a big box.

If staining persists before repainting (unless one wants to) it should be cleaned, well buffed out, then use a polish/sealer to treat/seal the porous gel coat surface, then Colonite!!