Black Stuff will not come off

Skip ThunderBolt

Skip ThunderBolt

New Member
Nov 16, 2022
18
Louisville KY
Boat Info
390 Sea Ray
Engines
2 454 Mercruiser
Hello All,
I am having a heck of a time removing this horrible black stuff off my 390. I even hit it with my power washer. Any advice? Thanks
 

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Not familiar with ON/OFF hull cleaner, but otherwise I would say

If it is embedded mold/mildew or the like, in the porosity of the gel coat . . . Tilex
If it is something else, next up would be SnoBowl or the The Works, both toilet bowl cleaners.
The second being a generic, but just effective version of the first.

In my experience, it seems that because Acetone strips any wax and/or sealer(s) from the surface, it's use leads to an increased probability of having a re-occurrence, especially were mold/mildew is concerned.
 
That looks just like diesel soot staining. Were you next to an old smudge pot that was spraying generator exhaust on your boat? Starbrite Instant Hull Cleaner. Safe on the Gelcoat. Wax afterwards mandatory.
 
You can also try Barkeeper's Friend soft cleaner. Also works great for cleaning stainless. Wax afterwards.

-Kevin
 
Yendor said:
Not familiar with ON/OFF hull cleaner, but otherwise I would say

If it is embedded mold/mildew or the like, in the porosity of the gel coat . . . Tilex
If it is something else, next up would be SnoBowl or the The Works, both toilet bowl cleaners.
The second being a generic, but just effective version of the first.

In my experience, it seems that because Acetone strips any wax and/or sealer(s) from the surface, it's use leads to an increased probability of having a re-occurrence, especially were mold/mildew is concerned.
Click to expand...

https://www.crcindustries.com/on-off-hull-bottom-cleaner-32-fl-oz/
 
ttmott said:
That looks just like diesel soot staining. Were you next to an old smudge pot that was spraying generator exhaust on your boat?
Click to expand...
I was wondering the same thing. Roll Off is another product that's good on diesel soot - but if the soot has been there for some time (which it looks like it has?), Roll Off may not cut it.
 
SKybolt said:
https://www.crcindustries.com/on-off-hull-bottom-cleaner-32-fl-oz/
Click to expand...
After watching this thread progress yesterday, I went looking and found it on Ebay, and only then came to the realization that it was a CRC product. After regrouping my search, I found it locally at the O'Rielly's in town here, and at a better price w/o shipping. Quite a rare occurrence for my little flea-bag town!
So now I have some without really having an immediate need for it, although that can safely be expected to pass before very long. Thanks!
 
Yendor said:
After watching this thread progress yesterday, I went looking and found it on Ebay, and only then came to the realization that it was a CRC product. After regrouping my search, I found it locally at the O'Rielly's in town here, and at a better price w/o shipping. Quite a rare occurrence for my little flea-bag town!
So now I have some without really having an immediate need for it, although that can safely be expected to pass before very long. Thanks!
Click to expand...
It's good stuff. Excellent at removing stains in the gelcoat from the water, too. BUT, it's essentially hydrochloric acid so take precautions.
 
Something in common with that other stuff I mentioned earlier, I would imagine. We live on the River where the Cypress Trees put a large amount of tannic acid in the water which makes for 'a hell of a tough to remove' bathtub ring on the airboat (and how I arrived at that other stuff). Be interested to see how this works on that, but he is out of the water right now getting new stringers and taking a backseat to the 270, so that test will have to be up the road.
 
Yendor said:
Something in common with that other stuff I mentioned earlier, I would imagine. We live on the River where the Cypress Trees put a large amount of tannic acid in the water which makes for 'a hell of a tough to remove' bathtub ring on the airboat (and how I arrived at that other stuff). Be interested to see how this works on that, but he is out of the water right now getting new stringers and taking a backseat to the 270, so that test will have to be up the road.
Click to expand...

Yup, very familiar with the "ring around the boat" :)

I don't have experience with those other two but have heard others talk about them. If they don't have HCL (muriatic acid) then maybe they have oxalic acid? Oxalic works very well, too, and is much safer. I've been using Slimy Grimy for years for stuff like this (oxalic is the main ingredient). It's more expensive, but comes in a tub of granular powder and mixes up to make a large amount.
 
Start off with something like Spray Nine, or Spray Nine Marine Degreaaee and a sp9nge and hose .
 
Good Morning All,
Thank you so much for all the advice! I love our community. I am off to O'Reilly to grab a few different products. I will report back with a product reviews. Thanks again for the help.
 
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