Hull stain removal

I've been restoring an '85 H16. I've applied gel-bleach products, (six times) sprayed on bleach and water mix,(three times) and used polishing compound made for light to medium oxidation on buffer pads. Still, after many attempts of scrubbing and rubbing, I cannot get rid of deep staining.

This boat had spent years moored during summer months on fresh water pond. You can see the original staining as it was when I picked it up. Funny how the darkest is now the lightest.
The second photo shows what remains after all the attempts.

Any ideas on how to clean it up to get the hulls really white again??

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'89 H14 'Jaws'
'85 H16

Try FSR?

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Matt Miller
Former - Director of Parts and Accessory Sales
Warranty and Technical Support
Hobie Cat USA
(Retired 11/7/2022)

Wet sand it?

I would check the hulls really well for soft spots before putting too much effort into it. If it sat for years in the water, there’s a good chance the fiberglass/foam is waterlogged.

sm

I would try some Slimy Grimy....it works great.

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Bill 404 21SE

The hulls are solid. No issues.
I guess I'll try fsr or slimy grimy as they are both oxalic acid products. Getting sore arms from all the scrubbing... Thanks for the ideas

Isn't fsr and Starbrite gel hull cleaner the same thing as they are both oxalic acid cleaners? Different %?

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'89 H14 'Jaws'
'85 H16

Short of a new coat of white gel coat or white paint, you’re most likely going to be able to mitigate the staining but not remove it. Gel coat is relatively porous on the surface and old gel coat even more so. The staining is now part of the gel coat which means you would need to wet-sand the hulls and see if that helps as SRM suggested. It’s tedious. I’d also consider a buffer and a heavy cut compound but you need to know what your doing or you’re gonna cut through to the glass beneath. Maybe you can find an abandoned boat to practice on (there’s sunfish littered all over the place around here).

That all said, I did wet sand and polish my 20yr old boat and it looks good (whiter and shinier) but when I touched up the bottoms with some new gel coat it’s obvious that new white is a LOT whiter than clean old white. So you can only do so much…

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H16 2002 "Islands" Sail No. 107432

Oxalic acid based is the first choice

Hoping your polishing compound didn't close up the pores

Hit it several times with Bar Keeper's friend (oxalic base)
Put powder on thick by wetting until it sticks, let it sit, scrub with short bristle brush, and repeat

If that fails your next option is wet sanding

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1984 H16 "Mister Rogers"
1984 H14 "Sundays"
2000 H20 "Jet"
Sheet In, Max Out

Thanks everyone for your thoughts on this.

I'll probably just finish polishing it this year to remove oxidation and wait until the off season to turn the hulls over and give them a hard compounding and wax. The hulls have been hit hard with the oxalic acid products already, and I don't see the benefit of "one more time".

Now on to re-riveting the front beams to corner castings (rivets loose) and adding corner blocks and cleats for the jib traveler upgrade... wish me luck!

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'89 H14 'Jaws'
'85 H16

I like to use Goof Off Outdoor Rust Aid. Dilute it with water in a hand held plastic 1 gallon hand pumped sprayer, spray it on, wait 2-3 minutes, rinse off. No need to rub or scrub. Recommend eye protection.

Safe for fiberglass/gelcoat.

Easily removes rust and organic stains (humic, tannic and fulvic acids, etc.)

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Tim
84 H16
82 H16
87 H14T
Tortola Sails: 115222
Blue Prism Sails: 88863
Clearwater, FL

Thanks Tim,

Other than the bleach, all the other products I've used are oxalic acid based which this one is well. However the hydro fluoride addition in this one may be different enough to get at these stains.

I've taken care of the corner cheek blocks for jib track traveler. Now I think I'll take the trampoline off, it's white, clean it, and then wet the lacing and lace it back up snug using a ratchet across the side beams to pull it in a little.

I appreciate your thoughts on this. Thanks again

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'89 H14 'Jaws'
'85 H16

Just wanted to update the stain removal process for future forum users as to my experience.

First up was a good wash and rinse.

I used Starbrite gel hull cleaner (oxalic acid) multiple times. It was probably the most effective of all, excepting the final winner. I liked the gell product for not just running off. Not a bad product.
Then it was on to bleach and water, in increasing strength, up to straight on bleaching. Repeated this three times with no effect at all.

Tried another oxalic product (FSR) with no further brightening of the hulls. Washed and rinsed, back to the drawing board.

Bought buffer pads and hull polishing compound meant for light to medium oxidation and cleaning. Smoother surface with oxidation removed, but no cleaner.

Finally, today the winner! Muriatic acid (hydrogen chloride) available at most hardware stores for $9. I used 1 pint to 1 gallon of water for solution. Used in well ventilated outside area, had protective gloves on and wore eye protection. Just sponged on liberally and waited 20-30 minutes before rinsing well including the trailer it was on. No rubbing or brushing.

If anyone goes this route, please heed the warnings of using this product. Simple, fast and effective for a 36 yr. old cat in need of well deserved cleaning.
Before:




After:

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'89 H14 'Jaws'
'85 H16

Wow! Looks great!

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H16 2002 "Islands" Sail No. 107432