Harbor Safe Marine Care Products
Waxes, Cleaners & Polishes

Marine 31 Mildew Stain Remover Gallon & 20 oz. Combo

Marine 31 Mildew Stain Remover Gallon & 20 oz. Combo
Money-saving combo includes gallon plus a full 20 oz. bottle!

Marine 31 Mildew Stain 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 Stain Remover forgoes volatile cleaners and instead relies on smart chemistry; even the most severe mildew stains are no match for the incredible cleaning power of Marine 31 Mildew Stain Remover.

Marine 31 Mildew Stain Remover is the best boat mildew cleaner available!If you’re a boater, chances are you’ve dealt with the seemingly lasting results of 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 stain cleaners. Fortunately for you, we’ve compared Marine 31 Mildew Stain Remover against other marine stain removing cleaners and have found that it removes mildew stains faster, with less effort.

Not all marine mildew stain removers are created equal! Most over-the-counter marine mildew stain cleaners rely on heavy concentrations of bleach and other volatile chemicals that actually cause more harm than good. But Marine 31 Mildew Stain Remover removes stubborn mildew stains without discoloring, dulling, or drying out vinyl surfaces.

Use Marine 31 Mildew Stain Remover on:
  • Vinyl cushions and chairs
  • Rubber fenders
  • Fiberglass
  • Gel coat
  • Canopies
  • Boat tops
Marine 31 Mildew Stain 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 Stain 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 Stain Guard to protect treated surfaces.
Includes 128 oz. and 20 oz. bottle with sprayer.

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 Stain Remover Gallon & 20 oz. Combo
Item #: M31-372-COMBO
Our Price: $71.98
Sale price: $57.99 - You Save $13.99 (19%)
Availability: Usually ships the same business day

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Product Reviews

52 Reviews
94% (49)
2% (1)
4% (2)
0% (0)
0% (0)
98% Recommend this product (51 of 52 responses)
Isle of Palms, SC
Stuff is amazing. Spray on and walk away. When you get back the seats are clean. We are now using it on our bathroom shower tiles. Same results!
Hot Springs, Arkansas
Quick Cleanup
This is my 2nd order for Marine31. My boat cleaning time is cut in half by using this product. I highly recommend!
ProsWorks fast and lasts longer
Ocala, Fl.
WOW! A product that actually DOES what is states!
I investigated your product and received my order last week. I'm not only hooked, line and sinker. I swallowed the rod and reel also. This product worked perfectly with a minimum amount of scrubbing. It removed mildew stains from my pontoon boat upholstery that have been on it for years. My boat looks new again. After trying numerous products with fantastic claims, this product out-performed them by a very wide margin. You have just gained a lifetime customer. Thank you!
Springville, Tennesse
Kick A** product!!!!
I wish I had taken pictures before and after I put my boat up for the year. People if your looking for a product to clean the interior of your boat this is the product for you. I'll be honest I was skeptical about this being just another expensive product but let me tell you, IT WAS NOT!!! Marine 31 did EXACTLY WHAT IT SAYS IT WILL DO!! The black spots on my interior had been on there since I bought the boat back in 2017. Today they are gone. If for whatever reasone they are back on there next year I WILL take before and after pictures to show you all the Marine 31 is the REAL DEAL!!!
ProsEverything about Marine 31!!
Plymouth, Mass
Marine 31 mildew remover
Product is excellent! Amazing how well it works. Gets rid of areas where pressure washing failed!
Appleton, WI
Worked excellent!!!
This cleaner worked amazingly well. I thought I would need to replace my boat seats. No effort, needed to reapply in some stubborn areas and use a bristle brush to scrub, but it got out 95% of the troubled spots. Couldn't be happier!
Really works!
Skip everything else! Been a boater for 50 years and dealing with mold spots is part of the deal. This is the only product I’ve ever found that actually eliminates mold with a simple spray. I will not be without it.
Awesome product!!!
Just spray on let sit for a few minutes then wipe down and all mildew is gone with zero effort. Great product!
South Carolina
Not sure if I will use this product again.
When I received this product, I found the seal on the gallon container had been broken. Product had leaked into the packaging though the leakage was limited so did not get outside of the outer container. There was a strong smell of clorox so left me wondering if the seal had been broken to add clorox to the the gallon container.

The spray bottle provided with the product failed after one day, so I have to get another spray bottle to replace it. The sprayer appears to be a very low quality.

The product worked quite well in cleaning the vinyl upholstery in our boat, so the end result was what we were looking to achieve.
ProsCleaned the upholstery as advertised.
ConsUnclear what chemicals are in this product. It seems to be mainly water and clorox, and if this is what it is, I can just make a 10% clorox solution to achieve this same result. Unclear who the manufacturer of this product is, so unable to look into the product formulation. I would not recommend this product without more experience with it and a better understanding for its chemical content. I will likely try Star Bright Mildew Stain Remover the next time to get a comparison.
White Lake, Michigan
Marine 31
This product is the most amazing product ever! We have lived with moldy stained boat seats for many years and tried everything to clean them. I purchased Marine 31 after watching some videos that looked exactly as bad as our boat that were cleaned up after using this product. This product works and works very quickly. Our boat looks like brand new again and it is almost 20 years old.
ProsWorks very quickly.
Rye, NY
works great
best product for mildew that we have ever used
Charlotte, NC
Finally! A solution that absolutely works
We've been trying for years to remove stubborn mildew stains on our boat vinyl. I couldn't believe my eyes. Literally spray and rinse away.
ProsWorks as advertised
ConsSpray bottle trigger broke on first try.
South Carolina
Product good but packing poor
The product itself seem to work very well however the seal on both bottles was eroded and the sprayer that came on the smaller bottle will not stay on and made me lose half of the bottle content when it popped off.

When a product cost as much that is a large waste! Hopefully they’ll get their packaging perfected.
ProsProduct was very good
ConsVery poor packaging which caused me to lose half of the product and the small bottle
Topsail Beach
Best product I have ever used for mildew
Getting mildew off my GradyWhite upholstery has always been really a tough job. Marine 31 made a huge annual spring clean up much more successful without the elbow grease. This stuff is a strong caustic so wear gloves! Recommending this to Atlantic Marine so they have it to sell and use on other Gradys
ProsVery effective and takes very short exposure to chemical to remove mildew
Naples, Fl
Marine 31 Mildew Remover
Great product. Works as advertised.
Grove, OK
Best product ever!
Marine 31 is the best product I've tried! This is not just for boats. I've used it on boats seats, metal railings, lawn furniture, decking, stone steps. etc.
Great Stuff!
Easily as good or better than any other mildew removers tried. Now if only they made a spider spot removal product. That's the worst of my cleaning problems.
New Port Richey, FL
This Stuff Works!
It's been a harsh winter so far this year in boating Florida -- and our boat seats showed it. Enter Marine 31 Mildew Remover! Great value dollar-wise with this combo offering.
ProsWorks! Well!
ConsNone, really. DO wear a mask ?€?. of course.
north Florida
It Works
This is the latest product I have used to clean up my 18 foot pontoon boat. To date it is the only one that actually did the job of removing mildew. Initially I thought it was a little pricey but since it works I would call it a bargain. Recommend.
ProsIt does the job
Consstrong odor
Ft Myers Fl
The Best
This is an incredible product that does everything that it claims! We purchased an pontoon boat in Florida that had seats that were almost black with mildew. We were contemplating getting new seats but decided to try Marine 31. We tried it and were shocked! The seats are now white and look new. The hard part is waiting for the 5 minutes to pass before wiping it off. It's actually quite fun using it. It should be named Miracle 31.
ProsVery easy to use.
Ramara, Ontario, Canada
I don't write reviews but this one just made my fingers do the typing.

I tried 4 others before Marine 31 - Starbrite, etc. Searched Google and saw Marine 31 sprayed on a boat seat with mold and watched it disappear without scrubbing. Ordered it and tried it on the seat of my jet ski and started out feeling disappointed because the mold did not come off as shown on the video. So, I a left it and lit a cigar, got another glass of champagne and wandered off to do something on the boat. About 15 minutes later I walked back to the jet ski to dry it off and put the cover back on and VOILA....AMAZING!! ALL the mold and mildew - GONE!! I wish I recorded the before and after. Will be happy to do a commercial for free....ha ha....great product! Thank you and best wishes!
Melbourne Florida
Amazing results
My boat is 20 years old. I’ve owned it for a year. The seats had mold stains. I tried every product on the market, and everything I could find on line to get the stains out. The stains remained. After reading several reviews about marine 31 I thought I would give it a try. The delivery was exceptionally fast. I tried the product immediately and could not believe the results. The newer mold actually disappeared before my eyes. The older stains started to lessen in color. And after several more applications the stairs were completely gone. This is an amazing product. As I said I have tried everything that I could research, and everything I could buy on the shelves. I thought my only option was to have the Seats Recovered. If you have tried everything to remove mold from Boat Seats and other similar items, do not let the price of the product deter you. I live in Florida, I believe it is the mold capital of the world. I would highly recommend this product to anyone who is fighting mold.
ProsWorks fast Completely removed mold stains Fast delivery Easy to use
ConsSlightly strong odor definitely want to use well ventilated as directed
BEST Product Ever!
I found this product by watching YouTube uses and reviews so I gave it a try. It is fantastic. It is the only mold and mildew cleaner I have found that really works and I've tried them all. The product does all the work. Just spray it on, wait a few minutes and wipe off the stains, mildew and grime. It is absolutely fantastic.
ProsEasy to use. Works great. Good price.
Works as advertised
When applied to dry vinyl and then left for a few minutes, the discoloration fades.
I used other products claiming to be “the only cleaner you need” and they did not even come close to the results of Marine 31.
I will buy this product again.
Powhatan Point, OH
I purchased an older pontoon boat and the seats looked awful with mildew. After watching a video of Marine 31 mildew remover I decided to try it. Do not hesitate buying this product. It works as stated and very easy to do. The seats look as good as new.
ProsEasy to use!
Works great
Made pontoon boat look new
White Stone, VA
Great Product
This is the best product I've used for mildew removal. It even refreshes the topside fiberglass.
ProsEasy to use. Works excellent.
ConsIf you miss a spot you'll know!
THIS STUFF IS ABSOLUTELY AMAZING!!!!! We have tried everything on our boat. Other chemicals only got some things out but not everything. Our boat still looked dirty!! We moved and unfortunately neglected our boat for 2 years because we were soo busy working on house. Our boat & seat cushions looked horrible! We wanted to clean our boat up good and start using it again. As a last option, we found this online and decided to buy it and give it a try. I'm telling you our seat cushions are now white as snow.....literally. It's amazing! And we are soo happy!!!
Citrus County FL
Works amazing on mildew
I found Marine 31 via YouTube. This stuff its amazing. I tried everything to clean up a boat I had just bought. This stuff with a 2 minutes speak worked where nothing else would.