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Protecting Boat Bottom in Brackish Water


Simon Williams asked:

Can VS 721 be used to protect an unpainted fiberglass boat bottom that I plan to store in brackish water for the summer season? I’m trying to avoid bottom painting my Mastercraft ski boat. It’s stored approximately 5 miles up a river inland from the southern NJ shore.



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Boat owners have had mixed results with VS721 in your part of the country. Brackish water will still support algae and barnacles so these can attach to boat bottoms and in some cases stain the gelcoat as well. VS721 will keep your bottom clean if you use your boat on a regular basis or if you wipe the slime off as it begins to appear. In this instance, bacterial slime is at the bottom of the food chain so if you can keep it off you will not be providing a host for algae and barnacles.

If you plan to leave your boat stationary in the slip for weeks at a time or if you allow slime to accumulate, growth will eventually attach. The benefit of VS721 is that it will seal the pores in the gelcoat against osmosis blisters and make marine growth much more difficult to attach and easier to remove. Even toxic bottom paint has limited effect at stopping growth on stationary boats in your area.

Those are your options. The reality is that as boat owners realize the damage they are causing to the environment, by polluting the water with bottom paints that leach heavy metals and neurotoxins into the water, they will seek alternatives before it’s too late and we completely destroy our planet. The oil leak catastrophe in the Gulf of Mexico is a stark reminder of what can happen when we try to take shortcuts and things go horribly wrong. Environment friendly alternatives, in some cases, will require more maintenance on our part. VS721 is one of those alternatives. The heavier the natural growth in an area, the more maintenance will be required.

If you can wipe the bottom from time to time, I would recommend using VS721 on your boat. If not, you can use bottom paint for the short term but understand that in the near future, it may be banned as it already is in parts of Europe and California.

Thanks for you question
Captain Aurora

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