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How to Remove Bottom Paint


Frank Asked:

Hi. I plulled my 1998 30′ cruisers out of the water and most of the paint is removed except for some spots. I want to strip it down and have it clear to apply your VS721 BOTTOM COAT. Do you have any products to remove the paint or anyideas about doing it before waxing.

I want to start next year with your product. The boat stays in the Hudson River and it’s right on the line of salt and fresh water, mainly fresh. I power washed it already and removed most of the paint and algae. Some of the white shows in a lot of areas. Is it OK to go without paint on the bottom and just use your VS721 BOTTOM COAT?



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To use The VS721 Bottom Coat successfully, your bottom must be free of paint, clean and shiny, free of pollutants or oxidation.

Before you start removing bottom paint, please be aware that this stuff is extremely toxic and can hurt you if you get it on your skin, in your eyes or breath the dust from sanding or spraying. Protect yourself with protective clothing, rubber gloves and boots, a face shield and respirator. You should also protect the environment by using a drop cloth under the boat to catch any residue and dispose of it in a proper facility for toxic waste. Prevent any paint dust from settling on other parts of your boat or on your neighbors boat, if you are working in a boat yard, because it will stain.

Also, check with your State administrators to make sure that you are allowed to legally work with this stuff and that you comply with all laws and regulations. Some States restrict or prohibit unlicensed persons from working with bottom paints because of the danger to people and the environment.

There are several ways to remove bottom paint:

I. Sanding, either wet or dry.
The benefit of wet sanding is that you can reduce the dust and by using finer and finer grades, get a fairly smooth finish. If you have a heavy build up of paint dry sanding or other methods may be required to get the bulk of it off. If dry sanding, a vacuumed attachment is highly advisable. When you get close to the gelcoat, switch to wet sanding to finish. To get it shiny again, you may also require rubbing compound. If you are lucky, your bottom will not have been rough sanded prior to the application of bottom paint.

It used to be common practice to scuff the gelcoat, prior to painting, to better hold the bottom paint. If this is the case, you will have to sand it smooth and then evaluate the remaining gelcoat to see if you have to refinish the bottom or if the gelcoat is intact. Remember that gelcoat is porous and sanding opens the pores even more. Open pores can lead to water migration into the fiberglass which can result in blistering. The good news is that VS721 Bottom Coat will seal the pores to prevent osmosis blistering.

II. Have the bottom soda blasted.
Soda blasting is similar to sand blasting, except baking soda is used because it is much finer and causes less damage to the gelcoat. This process will still leave a texture on your gelcoat which you will have to wet sand and or compound to get smooth and shiny again. This process will also open up the pores.

III. Using a chemical stripper
There are numerous ones on the market made especially for fiberglass boats. DO NOT USE HOUSEHOLD PAINT STRIPPERS. They will attack the gelcoat as well as the paint and ruin your boat. They are a less popular method because they are slow to work and are messy. It can take 2 to 12 hours of waiting and multiple coats, depending on how many coats and what types of paint are on the bottom. If your anti-fouling paint is mostly worn through, this may be the preferred method for you.

Due to the complexity, health risks and unpleasantness of removing old bottom paint, most boat owners just apply new paint over old until the problem becomes intolerable. Sometimes as many as 8 or 10 coats. This practice adds weight and drag to the bottom, which reduces speed and performance and increases the amount of fuel required to push the boat through the water. As soon as you remove the bottom paint, you will notice that your boat will run faster and easier and go a lot further on a gallon of fuel.

Once your boat bottom is clean and smooth, application of VS721 Bottom Coat is fairly straight forward and easy. There are no environmental or health concerns.

1. First prep the surface by scrubbing it with Boat Scrub and rinsing it clean.

2. Next rub in the VS721 Bottom Coat, using a damp sponge.

3. When it dries to a haze, wipe off the haze with a terry towel or soft cloth.

4. After 24 hours, apply a second coat, the same way.

5. Wait 48 hours and launch your boat.

You can also protect outdrives, shafts, transducers, through hulls, trim tabs etc. with VS721 Bottom Coat.

During the season, if you see slime starting to accumulate, take your boat out to a sandbar and give the bottom a wipe with a sponge or knock off the slime with a deck brush from the dock from time to time. Regular use of your boat will keep the bottom clean, except for the transom, where you do not get water turbulence.

Not only will your boat look better and improve in value, without the paint, but it will get on plane easier, run faster and save you fuel.


Thanks for your question,

Captain Aurora

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