Harbor Safe Marine Care Products
Waxes, Cleaners & Polishes

Marine 31 Mildew Remover 20 oz.

Marine 31 Mildew Remover 20 oz.
Remove stubborn mildew stains – FAST!

Marine 31 Mildew Remover quickly and safely removes stubborn mildew stains on virtually all marine surfaces, including vinyl seat cushions, rubber fenders, fiberglass, gel coat, canopies, and more! Marine 31 Mildew Remover forgoes volatile cleaners and instead relies on smart chemistry; even severe mildew growth is no match for the incredible cleaning power of Marine 31 Mildew Remover.

Marine 31 Mildew Remover is the best boat mildew cleaner available!If you’re a boater, chances are you’ve dealt with stubborn mildew stains on vinyl cushions. If you’re reading this product description, chances are you’ve been less than satisfied with the performance of other so-called marine mildew cleaners. Fortunately for you, we’ve compared Marine 31 Mildew Remover against other marine mildew cleaners and have found that it removes mildew stains faster, with less effort.

Not all marine mildew removes are created equal! Most over-the-counter marine mildew cleaners rely on heavy concentrations of bleach and other volatile chemicals that actually cause more harm than good. Marine 31 Mildew Remover removes stubborn mildew stains without discoloring, dulling, or drying out vinyl surfaces. Best of all, it still retains the powerful cleaning ability to remove mildew stains – FAST!

Use Marine 31 Mildew Remover on:
  • Vinyl cushions and chairs
  • Rubber fenders
  • Fiberglass
  • Gel coat
  • Canopies
  • Boat tops
Marine 31 Mildew Remover works wonders for household cleaning as well! Use this professional strength formula to clean tile, grout, showers, bathtubs, counters, and sinks.

Marine 31 Mildew Remover works FAST!Directions:
  1. Spray directly onto surface and allow 1-3 minutes for penetration.
  2. If necessary, agitate surface with a brush or terrycloth towel.
  3. For stubborn stains, allow cleaner to penetrate for 5 minutes before agitating.
  4. Thoroughly rinse and dry surface.
  5. Follow with Marine 31 Mildew Guard to protect treated surfaces.
20 oz.

Made in USA

Federal regulations prohibit the shipment of this products by air, UPS 3 Day, UPS 2, or US Mail. This item is shipped by UPS Ground only. Sorry but no APO or FPO addresses.

Marine 31 Mildew Remover 20 oz.
Item #: M31-370
Our Price: $21.99, 4/$65.97
Availability: Usually ships the same business day

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Product Reviews

169 Reviews
87% (147)
4% (6)
2% (3)
4% (7)
4% (6)
89% Recommend this product (150 of 169 responses)
Pittsburgh, PA
Magic in a bottle
We pulled our boat out of storage last week and all the vinyl was covered in mold and mildew. After 2 hours of scrubbing with mold and mildew remover and then trying a magic eraser - I was very upset thinking we would have to have the cushions recovered. The mildew had stained all the cushions and I couldn't get them to come off. I found this product online and figured I would try it before searching for someone to recover our seats. This stuff is MAGIC! I didn't even have to scrub the spots. It took awhile for the stains to disappear - but after about 15 minutes - every single spot was GONE! I will buy this product every year - and I am going to try the mildew preventer before we put the boat away at the end of the summer. HIGHLY recommend this product!!
Lillington NC
Marine 31 Mildew Remover
Absolute wonderful product. For health reason, boat sat for two years in North Carolina's humid, moist weather. Was covered with canvas boat cover for 1 year. Last year sat out in elements uncovered. In effort to clean, I researched internet and decided to test four methods of removing mildew: 1) Marine 31; 2) 3M mildew remover; 3) comet spray gel (vinyl only); and 4) magic eraser. Applied all 4 products to boat platform, left for 5 to 10 minutes. Marine 31 results were unbelievable. Person that was helping me could not believe the difference in the results as compared to the others. Family and Friends that have visited, I take them out to see the boat. Also boat owners, they understand the effort and frustration in trying to removed mildew/mold. Needless to say, they have ordered the Marine 31 to clean their pontoon. The mildew//mold on platform was heavier, darker, and thicker than what is shown in the cushion pictures below. It was just the only items I didn't get cleaned before I ran out of Marine 31 and have reordered. A picture is included to show how great the platform looks now. Like New. It was only when I was reordering to complete the project (cushions shown) that I decided I had to write the review. So wish I had a before and after on platform. Writing reviews is out of character for me, BUT I had to let others know. I have invested too much time in previously cleaning our boat and by no mean got the results obtain with Marine 31. The Marine 31 actually removed the gray spots left from previous cleanings where mildew stain could not be removed. The boat is a Renken (oldie but goodie) with lots of wonderful memories. My excitement from using the Marine 31 Mildew Remover has given me such confidence in this Brand that I will be ordering their oxidation products.
ProsQuick, efficient, and does the job. Spray on, leave 5 to 10 minutes, wipe off Cleans much older (gray) mildew stains that were left when previously clean the boat (3 years ago)
No Joke! It works!
We bought this product after seeing videos online of success. We were skeptical that we would have the same results but we were surprised! It worked just like the videos! We showed my in-laws and they immediately wanted to get some for their RV. That got me thinking about our RV so I ordered the gallon!
ProsWorks perfect! Spray it on, wait a few min, lightly agitate for stubborn spots, then rinse
ConsIt will take color out of your clothes. No big deal. Just wear old clothes and be careful.
Mineral VA
The Best
This product has cleaned a number of areas in and around my boat that turned black from mold.
I has safely cleaned the vinyl seats and the cloth like fabric on the ceiling of the head room. Even on our dock's bumpers where it would not completely clean off with a power washer.
Rhode Island
Mildew removed!!
Didn’t think it would help much but it made my boat cushions look new!!
, Dadeville AL
Works great!
Easily removed the mildew from my pontoon seats.
Paynesville, MN
High Expectations
In light of the $21.99 cost of Marine 31 and another $10.00 shipping I was skeptical to say the least of how this product would preform. I tested it on some lawn furniture before cleaning my boat. It blew me away how well it worked and it was safe enough for my 14 year old granddaughter to use it. The directions said for stubborn stains to let stand for 5 minutes but by 3 minutes the product was drying and we had to scrub so the really deep stains were 90% removed. That said I will purchase this product again.
ProsIt?s safe and easy to use.
ConsThe cost per ounce is high.
Its a life saver!
Works so fast and doesn't seem to hurt the fabric if you follow the directions.
Hartford, WI
Removes molding from old boat!
We have a 17 year old pontoon with white seats, which have developed mold on them over the years. Even a first pass on the seats with this spray, the stains either came out completely or faded the green/gray stains drastically (depending on the severity of the stain). Will definitely be buying this product again for touch ups!! A great way to refresh the look of your seats.
Great stuff!!
Great for cleaning mildew on boat.
loved it!
used on a coleman saluspa portable hot tube.Nothing worked,tried everything.Went on utube
and someone in florida bought a boat needed tlc?€?.he used marine 31,and it looked brand new...so I purchased marine 31...works amazing,and also on a pelagan kayak cleaned up in seconds!
Dadeville, AL
Awesome Mildew Remover
Awesome stain remover. Just spray wait a second and with a damp cloth boat seats come clean!
Fairfield Bay, AR
Saved Several Hundred Dollars
I think I may have already reviewed the product, but it is FANTASTIC! It saved me several hundred dollars in upholstery costs. I bought a vintage pontoon boat that had 30+ years of mildew spots on the furniture. We were in the process of obtaining an estimate to recover the the furniture including two pedestal chairs and the captain's chair. After using Marine 31 Mildew Remover, we no longer need those chairs recovered. I have never seen any cleanser work like this, and I've now ordered a gallon for future use. Worth every penny.
ProsFast service Excellent product
ConsWear good rubber gloves, or your hands will smell like bleach for days.
Great Product
Wish I knew about it sooner! I didn't even have to scrub the boat seats. Sprayed it on and the stains magically disappeared.
Atlanta, GA
Smells like Chlorine Bleach
The product description implies it does not contain bleach but is carefully worded and a bit deceptive. You should be more transparent about the chemicals being used. Smells and feels like bleach to me.

I will NOT use this product on the vinyl cushions of my boat. The search continues for a mildew and mold remover that won’t destroy my cushions in the process.
Very expensive bleach
Like many boaters I spend a an inordinate amount of time and money trying to keep my boat looking as good as it can be. I watched a number of YouTube videos where the black dots appeared to have melted from vinyl seats and hatch covers. This chemical smells like there is a lot of bleach in it which is fine. It really did not clean any better than Tilex or any other product on the market. It is fine, but NOT for the high price.
St Charles Illinois
This product is unbelievable it’s really a miracle in a bottle. I was skeptical that anything would work on those cushions because they were black covered in mold so I did not take a before picture and I am so sorry about that but this product really came through and it does exactly what it says it does don’t be fooled by couple of bad reviews . WOW. JUST WOW!!!
ProsEasy to apply, works fast, scrubbing is optional
Forked River, NJ
Amazing, incredible, unbelievable, best thing in the boating world, works on lawn furniture, it is from the Gods.

The product worked amazingly I highly recommend it to all boaters, pool furniture, and house siding. It works!!!
Just give it time to work, and boom Clean!
Didnt work that great
Didnt spray well and when it did spray hargly anything would come out. After spraying for 30 minutes i stopped and still have over 3/4 of bottle left going to waste
ProsNot enough to go on
ConsWaste of $20
works like advertised
Will keep buying
ProsAll pros
ConsNo Cons
Works like magic
Didn’t think my seats were going to come clean after trying didn’t cleaners but this one worked.
Lake Lanier, GA
Works Great!
2nd year that I’ve used the mildew remover. Works fast, works great!
ProsSimple application Minimal scrubbing needed Doesn?t hurt fabric
Gainesville, GA
worked as advertised
had very dingy mildew laden white and tan seats. Sprayed on as directed and worked great.
try not to overspray on fiberglass as it turned a little brown but came off with some rubbing.
Hilton Head Isl., SC
Great product!
The mildew remover is awesome..it removed all the stubborn mildew stains that were on the fiberglass and seat covers...
Boat looks brand new! Thank you!!
Dagsboro, De.
Removed my mildew issues off my vinyl.
Let it set for a few minutes and wiped off. Mildew was gone.
ConsNeeds to be done in well ventilated area. Strong Oder of bleach.
Jacksonville, GA
Mold/ Mildew remover
Searching for a product to remove stubborn mildew and mold stains. Came across this and decided to pay more for product to think a higher quality would work better and was not satisfied. Did not remove mold or mildew on my vinyl seats. Really just like using regular bleach that was over priced.
Although it worked well with my bathroom tile for cleaning but this was not the intention for buying product. Will use other products for cleaning bathroom, etc for cheaper.
San Jose, California
Miracle Mold remover!
Wow. I read reviews and decided to take a chance on this product, but was skeptical going in, to be honest. I had boat cushions that smelled bad and when I pulled the fabric off the foam pads, both the fabric and the foam were covered in black mold spots. When I got the Marine 31, I sprayed it liberally on all the mold and barely had enough product to cover all the area I needed. I then went to find a brush so that I could try to agitate and rub it in, per the instructions. When I came back with my brush, I was BLOWN AWAY!!! There was no mold visible anywhere!! How?!!! Holy cow chemistry is cool. My next step was to just thoroughly rinse everything and put it in the sun for a week to dry. Absolutely incredible product. So glad I know this exists, so that if it ever happens to me again, I will know what to do.
ProsAbsolutely amazing product. Spray it on. 5 minutes later the mold just disappears.
ConsIt's a chemical. Wear protective clothing, safety glasses, gloves. Do the work outside with lots of ventilation.
Mildew Remover
Just like bleach. Only bleach is a Hell of a lot cheaper. That's what it smells like also.
If you want something to make your life 1000 times easier when removing mildew off any surface, this is the product. It will clean battery boxes, t-tops, cushions, non-skid, and also anything not marine. This product will legitimately knock mildew out with one simple spray! Keep up the good work Marine 31!
ProsEasy to use. Tough on mildew. Very well priced.
Worked great. Only took minutes to kick in and wiped right away.
ProsTook stains off with no effort or scrubbing.
ConsOdor of bleach that lingered.