Stubborn Exhaust Stains

[Ian_Rob]

A 10 %- 12% concentration of Oxalic acid worked well (as it always does) at removing the yellowing we get at the waterline but there are very stubborn black stains at and about the exhaust outlet that persist. Is there an equivalent ’miracle‘ cleaning product that might remove them?

 

[Refueler]

I have an engine that insists on blacking out the world when pushed .. and know your plight well.

The secret is to not let it stay ... literally at end of each trip - I get the brush and dunk in the water ... brush away the loose stuff.

Later if the usual Domestos / Bog Cleaner doesn't remove the stain - then its oxalic or T-Cut. The Oxalic needs to be in paste form so it stays where applied to work .... mix in some wallpaper paste to it to create the goop.

 

[oldgit]

I have an engine that insists on blacking out the world when pushed .. and know your plight well.

The secret is to not let it stay ... literally at end of each trip - I get the brush and dunk in the water ... brush away the loose stuff.

Later if the usual Domestos / Bog Cleaner doesn't remove the stain - then its oxalic or T-Cut. The Oxalic needs to be in paste form so it stays where applied to work .... mix in some wallpaper paste to it to create the goop.

Recently tried a recent forum suggestion to use washing up liquid with Oxalic xtals . might have been a bit more enthusiastic with the "Fairy" than the recommended "few drops" in bucket and put in loads.
The results were excellent and without the wall paper paste gooey lumps and bumps.
The washing up liquid may well have shifted a few marks and stains as well going on the the hull evenly.
Put it on with broom and bucket and left it to get on with the job while taping up and anti-fouling.
250g from ebay. £13.00.
Bottle of Fairy £1.50.

 

[Refueler]

"250g from ebay. £13.00." ?????

Sorry to say this - but you were ripped off ..... I paid 11 quid all in .. incl shipping for 1kg.

Here's another as my seller is not listing Oxalic at present ...

Acide Oxalique 1000 grams 1 Kg 2,20 lb Sac Scellé Livraison rapide | eBay

Since buying mine ... pal of mine found an industrial supplier in Riga selling the stuff at less than 5 euros a 500gr bag ... Its actually used by many commercial people and I'm sure that UK will have such suppliers as well ...

 

[38mess]

The trouble with oxalic acid I have found after using it for years on my white plastic hull is it seems to remove a minute layer of the gel coat. Stains then are able to soak in better and it seems to get dirtier a lot faster. My problem was a yellow sheen which would appear after around a month of being in the water.

 

[Ian_Rob]

The trouble with oxalic acid I have found after using it for years on my white plastic hull is it seems to remove a minute layer of the gel coat. Stains then are able to soak in better and it seems to get dirtier a lot faster. My problem was a yellow sheen which would appear after around a month of being in the water.

Year on year the yellow staining seems to worsen. I seem to recall that Vix Cox made a similar comment a few years back. I guess that there will be a nano-particle surface treatment that might help but perhaps awkward to apply at the hull/anti-foul interface?

 

[Refueler]

The trouble with oxalic acid I have found after using it for years on my white plastic hull is it seems to remove a minute layer of the gel coat. Stains then are able to soak in better and it seems to get dirtier a lot faster. My problem was a yellow sheen which would appear after around a month of being in the water.

I tend to agree that Oxalic can remove 'sheen or gloss' of Gelcoat - but I don't think it actually removes any gel. I have found that Polishing after Oxalic is usually the reason Gel is removed as its 'smooths' the surface to get the 'sheen' back.

 

[Bobc]

Try Cif.

 

[Refueler]

I agree. Year on year the yellow staining seems to worsen. I seem to recall that Vix Cox made a similar comment a few years back. I guess that there will be a nano-particle surface treatment that might help but perhaps awkward to apply at the hull/anti-foul interface?

Years ago were reports on various used to clean / polish hulls .. and the worst for yellowing were the 'colour restorers' such as T-Cut. Followed up by silicon based polishes.

Of course in more recent years - water quality has changed and the increase of yellow stained lower hull areas has become a problem.
My boat - you can follow the bow wave pattern above the waterline literally from it.

 

[38mess]

Year on year the yellow staining seems to worsen. I seem to recall that Vix Cox made a similar comment a few years back. I guess that there will be a nano-particle surface treatment that might help but perhaps awkward to apply at the hull/anti-foul interface?

I did hear or read that a good waxing after cleaning might help keep the stains at bay. But waxing opens up a whole new can of worms.
I now use a product call Grunt, it's supposed to be gentle on gel coat

 

[Refueler]

Try Cif.

The old Cilit Bang Lime and Rust Toilet Cleaner was the stuff to use ... but then 'greenies' forced the change of formula and now its no better than others.

 

[Ian_Rob]

I have never tried a diluted solution of Hydrochloric Acid but there was an owner of a large Princess at a marina we were based at a few years ago who swore by it……??

 

[Ian_Rob]

The old Cilit Bang Lime and Rust Toilet Cleaner was the stuff to use ... but then 'greenies' forced the change of formula and now its no better than others.

Do you happen to know what were the active ingredients of the original products?

 

[Refueler]

Do you happen to know what were the active ingredients of the original products?

Judging by the aroma ... I would assume something like Phosphoric Acid as part of it.

Phossy is used as a rust stain remover on ships .. well it was when I was a cadet !!

 

[AngusMcDoon]

When gelcoat gets old it gets a chalky porous surface layer where UV in sunlight has damaged it. You can see this if you rub your fingers over dry dull gelcoat - you end up with fine white dust on them. You may find something to remove the stain but while the porosity remains it will quickly come back. There's only one permanent solution - remove the porous layer. You can do this using 3000 grit or finer wet and dry sandpaper - gently and backed with a sanding block - until the stain is gone then bring the surface back to the original shine with a polishing compound like Farecla.

While this removes some gelcoat it's a tiny amount and only the surface that's damaged anyway. Redoing the process every 15 years there's enough thickness of gelcoat so see most people out.

 

[johnalison]

I use a strong detergent gelcoat cleaner, such as those from International or Starbrite, which removes most of the grey, and then follow with Starbrite Color (sic) Restorer Polish which removes the rest and it then matches the unstained white topsides.