hard water stains

[emitt1]

good evening all.  sitting here trying to figure out what i could use to get the hard water stains off my boat.  i fish lake erie and the boat just looks terrible on the outside.  going to put it away for the winter and just wanted to get it cleaned up.  any info would be great.  thanks...

[4426]

generally ill use lysol toilet bowl cleaner, the black label one that says " lyme and rust" on it. Go down the waterline with it applying a bead then spread with a soft bristle brush, let sit for a minute or so scrub again and rinse off(dont let it dry). may take an application or two. Back when i worked at a marina we would use a pump sprayer with it as well but same general idea

edit: this is assuming you're referring to a fiberglass boat that has been kept in the water for the season and youre dealing with the stains near the waterline

Edited October 16, 2025 by 4426

[emitt1]

well know,,,,,,,, its a alum,,,, painted and has a sticker on it.   

[4426]

I think people still do the same method, but you just need to become careful as it is an acid you’re dealing with and can definitely cause negative effects(definitely have left some chemical burns on my bare aluminum trailer). The painted surface *should* protect it. I would maybe start with a pressure washer with a wide fan tip, then go from there.

[rolmops]

I have a similar aluminum setup in Lake Ontario and this year I switched to a cleaner called "Slimy Grimy" .

It comes  as a powder and you mix 2/3 of a cup with one gallon of hot water. I went and bought a weed sprayer tank a Harbor freight, sprayed it on and let it sit for a minute. Then first with a power washer , but later also just hosed it down and it did miracles. It made me decide to not put bottom  paint on the boat. 

Edited October 17, 2025 by rolmops

[dickey]

For water stains on my aluminum boat I make a vinegar/water solution in a spray bottle. 50/50 ratio. My boat is trailered so my water stains are from water spray. 

[emitt1]

well thanks for all the help guys,,,,,,  i hopefully can get it cleaned up.  then to tackle the pluged up floor drains in the back

[Sk8man]

Although my boat is fiberglass I believe this also works on painted aluminum. It works great for most stains. It can be found online or most Walmarts etc. carry it in the boating section.

 

[emitt1]

ok,,, thank you for the information.   hate this time of year,,, not for the cleaning up part. but for the putting away until next year.  i hate the wait.  

[Shakemsam]

Cleaners like.. toilet bowl cleaner, 409, or actual hull cleaners, I use for algae stains. Hardwater stains can generally be removed with a wash and dry. I wipe down my OB with a Wd-40 throughout the season for a spotless finish.

[jk1]

Try the vinegar mix first.   50 50 with water, let it sit for 10 minutes.....jk

[emitt1]

thanks for all the help

[lrg355]

On 10/16/2025 at 8:26 PM, rolmops said:

I have a similar aluminum setup in Lake Ontario and this year I switched to a cleaner called "Slimy Grimy" .

It comes  as a powder and you mix 2/3 of a cup with one gallon of hot water. I went and bought a weed sprayer tank a Harbor freight, sprayed it on and let it sit for a minute. Then first with a power washer , but later also just hosed it down and it did miracles. It made me decide to not put bottom  paint on the boat. 

If you use very hot water with Slimy Grimey it works much better.  I always bring a large pot of water near boiling then do the mix in the sprayer.