Help with mold/midew, ozone machine, bilge/locker cleaning

Sep 30, 2025
173
Catalina 22 Davis Hollow - Lake Arthur
Bought a 1971 C22. Good shape for its age but it sat for years and very dirty and coat of mildew or old mold stains all over the "bilge" areas and inside lockers. I'm very sensitive to Mold and had ton of health issues from mold and (chronic lyme also for a decade) and just cant take any chances with any mold. I intend to sleep on this boat a lot.

Actually did not see any "MOLD" as I think of it. Not puffy, mold...just like a coating of who knows how old dirty mildew, stained, film.....blah... Didnt even realize how dirty it was until I started scrubbing and realized most parts were much lighter color "clean". Boat smells musty but not horrible. Took everything out, including all wood and bulkheads to check for wood rot (there was a tiny bit on bottoms).

I cleaned the heck out of "everywhere!!" I could possibly reach with the Borax (baking soda, borax, tsp, hot water) formula mentioned on here. Sprayed it, scrubbed it, wiped it, sprayed again. scrubbed again and left nice coating everywhere. (also been running box fans for weeks before and after cleaning) Smells much better now BUT... There's lots of areas I cant possibly reach. Up inside where the hull/deck/cabin joins are....Up in parts of the transom....under the cabin little floor "hallway".

I bought this ozone in hope it will kill!! the molds in these impossible to reach areas.


-How long to run it?
-Any tips for me here?
- Should the Borax solution with the film left behind work well in those areas I could reach?

-I plan to also paint the "bilge/lockers" areas with a 123 primer then rustoleum enamel oil based., good idea?

Thanks!!
 

Attachments

Last edited:
Jan 11, 2014
13,947
Sabre 362 113 Fair Haven, NY
To get to the hard to reach areas, use a garden sprayer and stick the wand up into those tight spaces. Don't worry about rinse or wiping off, just leave it there.
 

colemj

.
Jul 13, 2004
1,033
Dolphin Catamaran Dolphin 460 Mystic, CT
Another approach for hard to reach areas is chlorine dioxide. You can buy a kg of crystal powder on Amazon, as well as "kits" often sold as car or house purifiers. Put a few tablespoons in a bowl, add a little bit of water to cover them, put it low in the bilge then add a shot of muratic acid and close up the boat. Technically, there are stoichiometric quantities to add, but it really doesn't matter with this. Come back in a day and open the boat and let it air out. The ClO2 gas will permeate everywhere and kill everything. The boat will smell fresh, if not a bit like chlorine. Just dump the remaining liquid overboard, as it will mostly be table salt and water with at most a weak amount of muratic acid.

This is my go-to for this type of thing.

Mark
 
Sep 30, 2025
173
Catalina 22 Davis Hollow - Lake Arthur
Another approach for hard to reach areas is chlorine dioxide. You can buy a kg of crystal powder on Amazon, as well as "kits" often sold as car or house purifiers. Put a few tablespoons in a bowl, add a little bit of water to cover them, put it low in the bilge then add a shot of muratic acid and close up the boat. Technically, there are stoichiometric quantities to add, but it really doesn't matter with this. Come back in a day and open the boat and let it air out. The ClO2 gas will permeate everywhere and kill everything. The boat will smell fresh, if not a bit like chlorine. Just dump the remaining liquid overboard, as it will mostly be table salt and water with at most a weak amount of muratic acid.

This is my go-to for this type of thing.

Mark
Interesting. I never heard of that. Sounds promising. Is this a common thing that's done on boat?

Do you think that would do a better job than the OZONE at actually KILLING the mold spores that I can not get to?
-So would I make my batch stronger for something like this?

Will this damage anything? There's really nothing in the boat bu just curious and trying to understand.

Also, any thoughts on priming and painting the bilge/lockers to really seal those areas...and also make them harder for mold to grow and easier to clean.
 

colemj

.
Jul 13, 2004
1,033
Dolphin Catamaran Dolphin 460 Mystic, CT
Is this a common thing that's done on boat?
It is on ours. ClO2 is a common commercial mold and odor killer, as well as used to treat potable water.

Do you think that would do a better job than the OZONE at actually KILLING the mold spores that I can not get to?
-So would I make my batch stronger for something like this?
I think it does a better job than ozone because it doesn't dissipate as fast, nor reduce as quickly.

There isn't any "make it stronger or weaker", because it is a catalyzed reaction that goes to completion. You can use more or less to cover larger or smaller areas, but the "strength" is all or none. A C22 area would only take 4-5 tablespoons of crystals with maybe a 1/4 cup of water and a few tablespoons of acid. Close the boat up to keep the gas inside. Adding a circulating fan inside can help get it everywhere evenly.

Will this damage anything? There's really nothing in the boat bu just curious and trying to understand.
There are a few complaints online with people using this method in their houses and RV's about it bleaching the colors of their bath towels and curtains. I haven't found this to be the case with cloth materials on the boat, but haven't really tried it with bath towels and the like around.

It won't damage rubber stuff like ozone does.

Also, any thoughts on priming and painting the bilge/lockers to really seal those areas...and also make them harder for mold to grow and easier to clean.
Priming and painting bilge and locker surfaces is a great idea. Putting a hard, smooth surface on them goes a long way to keeping mold at bay and getting things clean.

Mark
 
Apr 11, 2010
991
Hunter 38 Whitehall MI
Be very careful with ozonators. The ozone produced is harmful to humans and can cause lung damage. So ventilate thoroughly before entering the space.

Ozone will also degrade plastics so use should be limited to only a short and very limited times. Amy plastic materials and boat components made of plastic can be damaged by the ozone.
 
Sep 30, 2025
173
Catalina 22 Davis Hollow - Lake Arthur
I am careful and understand the health warnings and concerns with the ozone... and the boat is gutted and completely empty. Just wondering how long I should run that particular OZONE model for to hopefully kill the mold spores in the impossible to reach spots so I don't end up getting sick again from mold exposure?

Also the chlorine dioxide that Colemj has mentioned sound like it might be an even better solution to my issue. Anyone else have experience with this?
I tried finding the kits but I only see ones for water purification...? Can you link me to a "kit" possibly?

Last question on my mind is I'm wondering about PH. The borax solution I mentioned I used everywhere, is very alkaline...which It seems is mainly why it is so good to kill and prevent mold (mold cant survive in that high of PH I guess?) My question is should I then stick to only Alkaline cleaners/mold killers with everything I try now. As I mentioned, 90% of the surfaces of the inside of the boat have been cleaned with the Borax formula and left with lots of film all over bilge and lockers to prevent mold. If I start putting say...vinegar or acidic cleaners on top of that, would I be canceling out the killing properties and actually undoing the prevention that I have? Is the Chlorine Dioxide method Acidic?... and therefore possibly a bad move in my case since I already went "Alkaline"?

Hope none of this sounds stupid of me . I'm just trying to understand. And I've have been stressing a lot about being able to sleep on the boat and still confident that my health is not compromised.

Thanks!!!!
 
Oct 13, 2020
200
catalina C-22 4980 channel islands CA
I have used an ozone generator on my C-22 I let it run for four hours. I left the forward hatch unlatched and when 4 hours were up I opened the all hatches and lazerett hatches and let it air out for a few hours before entering.
 
Aug 17, 2013
1,268
Pearson P30 202 Ottawa
On m’y previous boat (Grampian 26) I rented a fogger from Home Depot, filled it with Concrobium mold killer, closed off the boat, let it run for 4 maybe 6 hours, same principle as your borax solution, leave the film on and never had an issue.
keep in mind that boat was extremely covered in mold, had been on the hard with a broken window for over 7 years, so a lot of stagnating water inside.
 

colemj

.
Jul 13, 2004
1,033
Dolphin Catamaran Dolphin 460 Mystic, CT
Here is an example of a kit for a small space like a C22: Amazon.com

If you want to buy bulk and add your own acid: Amazon.com

I should have been more clear and said you are searching for sodium chlorite, and not chlorine dioxide. Sodium chlorite is what reacts with the acid to form chlorine dioxide.

The kits with tablets you add to water contain sodium chlorite and citric acid in the tablets, so water activates them.

Mark
 
Sep 30, 2025
173
Catalina 22 Davis Hollow - Lake Arthur
Yes. You posted while I was typing the above message.

Mark
lol.. I always have bad timing...

Thanks a boat load. Think I'll try it as long as the PH isn't going to effect what I already have working for me now...

I'm still wondering about the possible (balancing out) PH issues I mentioned earlier. Since I've been using the borax formula, I'm very alkaline in there and on all the surfaces as a film for prevention are alkaline. Is this stuff Acidic? If so would it neutralize my high PH prevention's and make that less effective?

Should I always stick to the alkaline Borax formula and not use things like (Vinegar....) in there now because vinegar is acidic and would neutralize things and loose my prevention?

THANKS FOR EVERYONE'S HELP!!! It sucks having to worry so much about mold but that's my reality now....
 

colemj

.
Jul 13, 2004
1,033
Dolphin Catamaran Dolphin 460 Mystic, CT
lol.. I always have bad timing...

Thanks a boat load. Think I'll try it as long as the PH isn't going to effect what I already have working for me now...

I'm still wondering about the possible (balancing out) PH issues I mentioned earlier. Since I've been using the borax formula, I'm very alkaline in there and on all the surfaces as a film for prevention are alkaline. Is this stuff Acidic? If so would it neutralize my high PH prevention's and make that less effective?

Should I always stick to the alkaline Borax formula and not use things like (Vinegar....) in there now because vinegar is acidic and would neutralize things and loose my prevention?

THANKS FOR EVERYONE'S HELP!!! It sucks having to worry so much about mold but that's my reality now....
The issue of pH with chlorine dioxide isn't relevant. Although the gas is formed under highly acidic conditions, that acid is confined to the container you mix it in, and is consumed by the reaction. The effectiveness of the gas itself, which does the work killing mold, is not dependent on pH, and won't be changing the pH of any surface it interacts with.

I understood that you got all of the surfaces you could reach cleaned up, and wanted to get to those surfaces you cannot access? Chlorine dioxide will be great for this. It will also take care of anything left on the surfaces you cleaned.

Don't use vinegar to treat mold. It kills the surface mold initially, but doesn't reach the roots in anything porous. It can also leave organic residue behind that is great future mold food. You've already approached this intelligently with the borax, so don't go changing to something less effective.

I think you will be happy with the ClO2. It will fill your boat with a dense, white fog of gas that will fill all spaces and sit in there for 24hrs. Make sure you close up the boat as well as you can, with tape or towels to shut off any openings like thruhulls, vents, etc. Then let it stew in there and kill everything. Afterwards it might have a slight bleach smell to it (I can smell it for several days after, but my wife can't smell it at all and she has a more sensitive nose than me), but you won't see or smell or react to any mold.

Mark
 
Sep 30, 2025
173
Catalina 22 Davis Hollow - Lake Arthur
Thanks Mark. You answered all my questions and helped me understand a lot of things I was hazy about. Truly appreciate your help.
 
Sep 24, 2018
4,448
Catalina 30 MKIII Chicago
I used to have an Ozone generator next to my bed. I had it on high one night and woke up unable to breath until I moved away from it.

I had a bad mold issue when we had an unusually humid July. After cleanup I wiped all wood surfaces with hydrogen peroxide to help prevent future issues. I also added solar fans. Only very minor occurrences after that.

Check out formula A and B. I haven't tried it but Practical Sailor rarely steers me wrong
https://forums.sailboatowners.com/t...missing-practical-sailor-magazine.1249942995/
 
Sep 30, 2025
173
Catalina 22 Davis Hollow - Lake Arthur
I used to have an Ozone generator next to my bed. I had it on high one night and woke up unable to breath until I moved away from it.

I had a bad mold issue when we had an unusually humid July. After cleanup I wiped all wood surfaces with hydrogen peroxide to help prevent future issues. I also added solar fans. Only very minor occurrences after that.

Check out formula A and B. I haven't tried it but Practical Sailor rarely steers me wrong
https://forums.sailboatowners.com/t...missing-practical-sailor-magazine.1249942995/
Yes, I've been using the formula B (Borax) one. Seems to work well for parts I can reach.

You ran ozone in same room while you slept? Thought you weren't supposed to even go in a room until its been completely aired out from ozone.
 
Mar 26, 2011
3,943
Corsair F-24 MK I Deale, MD
I came up with the "Formula B" as part of a test series for a magazine article 13 years ago. The editor asked if I could come up with something, so I scratched my head, tested about 15 commercial products and a few of my own imagination, and "B" came out number two, and number one as cleaner/biostat combo. (Number one was Goldshield--Google it--they make good stuff that lasts longer). I'm glad it has helped people.

Actually, the real reason for my interest was that I had a house that would periodically get wet carpets in the basement. I got good at cleaning, de-stinking, and protecting wet carpets. The mag article motivated me to get to the bottom of it. It sure helped me.

Another thing you might try is BAC (benzalkonium chloride). Wet-and-Forget is about 10%, which you dilute 100:1 to an effective concentration of 0.1%. It is commonly used in hand sanitizers. It's not a cleaner, but it will stay longer in a bilge where there is condensation. Also effective on carpets. Like the borax formula, you should NOT use a higher concentration.

---

My current boat has a wet bilge and fabric hull liners throughout, so every ~ 3 years I spray, scrub a few spots, and vacuum. That keeps it good. I also crawl the bilge, scrub what I can, hose down the rest, and then, after it dries a little, mist it with formula B. The hull liner looked like a Jackson Pollack painting when I got it, but it cleaned up like new.
 
Sep 24, 2018
4,448
Catalina 30 MKIII Chicago
You ran ozone in same room while you slept? Thought you weren't supposed to even go in a room until its been completely aired out from ozone.
I was young and dumb. I'm not sure how they're supposed to be used outside of a product aging chamber. I had a project at a building that had an industrial sized one for the dumpster in the dock. It helped keep the smell down but I got headaches if I spent a few minutes in there. It was a constant battle with people to keep it at reasonable level.