Getting Yellowish Stains Out of Your Hull – An Effective Method!

Over the course of the summer boating season, you’ll likely notice a yellowish gel stain accumulating in the hull of your boat.  This will be very normal and can even be a little more aggressive depending on the PH balance of the water you have your boat in.  This stain looks very ugly and can require some very strong elbow grease to take it off.  When you are talking about a boats entire hull, even the inside of the boat, it will quickly become a project you cannot do on your own.

I’d like to share a method that has worked very well for me in cleaning the hull of my boat.  There is a well known commercial boat cleaning product called Starbright and has a base chemical of Hydrochloric Acid (HCL).  This product does work well but there is something that I think works even better and has a base of Muriatic Acid.  It is a relatively easy process but you definitely want to be careful since you are working with concentrated acids.

Before you even gather the materials you need for this project, I would recommend applying a bleaching agent to the hull of your boat, which should help in removing some of the yellow grime that has accumulated.  After applying the bleach, let it dry off and rinse off the entire boat with water.  Let the boat air dry then get ready to watch the magic happen.


First things first, please make sure you wear proper protective eyewear and gloves.  Even one drop of Muriatic acid can cause severe irritation and damage to the eyes and skin.  Also, be sure to do this in a very well ventilated open space as the fumes are strong.  Once you have the proper protective gear, muriatic acid can be purchased at a local Home Depot or Lowes hardware store.  You will also need a spraying container similar to those found in the gardening section that apply weed killer.  Once you have all of the material gathered up, place 1 part muriatic acid into the container and 4 parts water.  I usually begin with 2 cups of acid and 8 cups of water, if I need to apply more then I simply add more of the same solution to the container.  Make sure to not fill the sprayer to the brim as you want to leave some air to create pressure for the pump.

Once you have the proper mixture in place, begin spraying the boat in sections.  You should see immediate effects take place in just seconds.  The yellowish/brownish gel stain should start dissolving away and the hull of the boat should look as if you just got a brand new paint job.  Slowly spray the perimeter of the boat making sure to go from top to bottom of the hull.  Once you have the entire boat complete you can re-apply another coat if needed.  If not, simply rinse the boat off and let air dry.  You’ll be amazed at the quality finish and you didn’t have to apply any elbow grease to get the stain off of the hull.  Enjoy and share with others who could use the tip!

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Posted by: admin on Category: Boating Tips