MK20128 On & Off Hull & Bottom Cleaner, 1 Gal

Worked like a charm so all of the water scum literally just rinsed off leaving a clean and shiny hull

It is highly toxic and corrosive to people, but it sure cleans a boat. Our boat is across from the gas dock and any spill goes all over my waterline. I couldn't get it off with anything, except MaryKate.

This product works great to remove the water tea stain. Wear gloves, eye protection and face respirator because it is very strong. Spray it on, rub lightly with a paint brush then rinse with water. Super easy.

This will take it off.. use on the jetski every year as well.. spray it on.. old scrub brush used to agitate it.. and rinse.. just don't breath the mist, you won't like it.. once diluted it just washes down the drains ect.. yearly staple cleaning your boat from the season of sitting in the water.

all good

Just cleaned the hull on my Sea Ray with this product. Did a much better job than the Starbrite Hull Cleaner. This product is potent - strong aroma of acid that will burn your nose. I wore gloves and used a paint brush to apply. Very fast results.

The product works great. Just wipe on with brush, let it sit for a minute and rinse off. I have it an extra rinse with a cloth and it really worked. Stains were gone. If using on a boat, I would recommend waxing right after.

Great product that works as intended, Work quick and make my boats hull look clean again

When my husband takes the boat out of the water for the season, he will use the boat cleaner. He knows it will work well because his friend had used this product before. He was very happy to find the product he was looking for !!

Works really well, best boat hull cleaner out there hands down....spray on, wait a couple minutes then wash off. Use in a well ventilated area, strong odour.

I've had this boat for over 10 years and spent quite a bit of money on many products that didn't work. This product worked for me with out a problem. I mixed a bit of it into a bucket with some water and I use one of those car mops with a handle. I soaked the mop in the bucket and scrubbed a dirty area on the boat. Then I got distracted for about a few minutes. When I looked back at the area it was clean. Nice! I continue to do the same thing over the entire bottom of the boat then I rinsed it off. I was very happy with the results.

Every year we struggled with cleaning the scum and water line off the boat hull after taking it from the water. That is until we found "On & Off". When I was purchasing, it said brush on and hose off. I thought "yeah, Right" but having struggled every year I thought I give it a try. The scum was dissolving as I was brushing it off and with little time and effort the boat hull looked great. You need to take the precautions listed in the directions. This is a powerful acid so make sure you wear what they tell you to wear and follow the directions.

I don't review much, but was just on Amazon ordering some more for next year, and was surprised that this wasn't that "popular.".Maybe most people purchase from local marine store (like I did first time).Anywhooo.... To the point: 1)-- when I was a teenager, end of each boating season, we cleaned hull of family runabout with series of rubbing compound, polishing compound, then fresh wax job (yeah, I know, "novices" or your choice of -facetious adjective.... you won't hurt my feelings).... and Pop, if you're reading this, I forgive you, and I don't think this experience is a component of my current close relationship with the chiropractor.2) later (and I won't admit how many years it took for us to "call-BS" on that approach), tried other products, then over time moved on to muriatic acid (WHICH THIS PRODUCT IS NOT--- but rather much more effective/efficient in my humble opinion).3 Summary editorial:A This stuff is the berries-- one of those "are you kidding me?-type products."B) combo of hydrochloric, oxalic and phosphoric acidsC) surprisingly used only 9/10th's of a 1 gallon bottle (yesterday) to clean entire hull of 25 foot Glastron GX255--**** that had been docked in fresh-water lake/reservoir for 5 months****D) "FOLLOWING INSTRUCTIONS": i). definitely gloves, eye-protection, mask (first 2 years I used a bandana, this time a 3M particulate mask--b/c I had a box in garage--- but, probably no better than bandana, since won't filter gaseous fumes--you can get a mask that will work, I just opt to "try" to be careful..... avoiding the "enclosed spaces" is the key--this doesn't just mean doing it outside--rather if your crouching/kneeling/laying partially under boat on one side, particularly if there is no circulation/breeze or if you are "downwind," you're gonna get a whiff of some choke-worthy fumes (sometimes the more concentrated fumes are briefly visible). ii) method of application-- see "E" belowE). Application: first year did it exactly as per instructions-- applied with paint brush, rinsed (I used an 1850psi cheapo-electricpowersprayer). Worked beautifully, BUT, 7-8 hours in long pants, LS shirt, bandana on face and head, vinyl gloves filled with sweaty hands, goggles fogging-up nonstop-- and I still found a way to get a couple small blisters under watch band and back of neck. I also know I inhaled the most fumes that year. If you do it this way, I found that a mechanic's dolly is a godsend (the thingyou lay on and roll around under stuff). --Second year--bought a telescoping-handled bristle brush. Better for your lungs and nasal passages, safer for your eyes and skin, but lots of wasted product, and somewhat challenging to apply without "honey, you missed a spot" (actually, I'm single, but most of you suckers are probably married, so figured I'd talk your lingo, no matter what your gender-- and if anyone researching this has 2 X-chromosomes..... WAY TO GO). --Third year--took it to detailing shop and had it done (think it was $200-300).--THIS YEAR: I'm sure many have thought of this before (I'm sometimes kinda slow)..... But my epiphany idea actually worked.... $6 garden/weed sprayer...... could adjust nozzle from mist to stream.... don't advise mist.... set it somewhere in the middle for the easy to reach places (kind of a "shower" spray for more uniform and complete application)...... adjust it more toward "stream" to get the harder-to-reach places. Now, could have been the cooler temp yesterday (45-50F), but we found that letting sit for 4-5minutes helpful-- previous years, when warmer, this stuff literally "melts" the algae / waterline stains off as you stare in amazement, mouth agape, over 30-60 seconds, then spray it off.Caveats / Final thoughts:1). Definitely needed good power sprayer yesterday (again, not sure, but suspect cooler temp?).2). First 2 years did it in driveway, discolored focal areas where prolonged exposure--kinda looked "cleaner" concrete--but was NOT permanent. Apparently, it's technically eating-away at the pavement?3). Put the pets inside4). Yesterday, after spraying on acid, initially used that bristle brush to "spread around" because some of the product was obviously dripping off of the hull (and I didn't know how far the 1gallon was gonna go)---- I think this approach actually wasted more product, cuz had to hit these areas twice. Once stopped using the brush, letting sit for few extra minutes, were golden.5). Product will "foam-up" a bit when it contacts the algae stains-- was helpful on dual-prop Merc outdrive, cuz lots of nooks andcrannies, AND because once fairly clean, realized when rinsed and air-dried, would still have some residual patchy area of smegma stains. Sooooo, rather than waiting for complete drying after rinse, I just lightly sprayed again and areas that needed more would foam up. Will also foam up on any rust (we have a trolling plate mount with some screws that aren't the best)-- so seems toclean the little bit of rust off of these.6). I use it on outdrive--takes a couple extra "spot cleanup" passes-- they sell an "outdrive-specific" product, I don't know if different or just marketing.7). I use it on props-- takes several quick applications.8 I havent covered trailer with plastic sheeting since first year..... I havent noticed any damage.... But, I'm sure it would with 5-10 minute exposure-- I did notice one silver dollar sized patch on diamond-plated side-step of trailer, where I'd ignorantly left a little puddle of acid probably 10 minutes--made it shiny probably took coating off.9). I DID NOT LIKE THE "GEL" Formulation of this product-- tried initially year #2-- just absolutely did NOT work for me.... evenwith repeated applications of various "incubation times."10). WHAT IF I GET THIS ON SKIN, IN EYES, ETC. -- obviously follow instructions, be smart and careful. -- but, only speaking in terms of my personal experience...... have gotten it on my skin numerous times (one nice thing is it's not insidious-- you'll know quickly, it starts to sting, and I've never had to do anything except quick 10-second water rinse) Got a face full of the mist a couple times yesterday (swirling wind)..... Coughed, closed eyes tightly, recoiled in Mild-moderate temporary discomfort...... splashed some water on my face and in my eyes..... nutted-up and moved on just make sure to remove your acid-splashed vinyl gloves first--- no, I actually thought to do this, surprisingly). And while i have donned eye protection 90% of the time while using product, I didn't have my goggles on when this happened, yep.11). If I remember anything else to bore you with, I'll add it later12). I'm not manic, and immodium AD does not help "verbal diarrhea"--but you see why I have to be selective with what I review13) I certainly have no affiliation to MaryKate OR Ashleigh, although the former should reimburse me at minimum wage for the 2+ hours it took me to "2-finger type" this on this frigging iPad.