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Nearly as much fun as that first spring cleaning, adding a coat or two of anti-fouling bottom paint is usually the last major chore undertaken before putting a vessel back in the water after a long winter in dry dock. Like scrubbing the deck, it’s a necessary evil, one that pays big dividends when it comes to getting under way.

Simply put, the primary purpose of bottom paint is to defend against plant growth, slime and barnacles or similar crusty creatures hitching a free ride on your vessel’s bottom. Unprotected, your hull below the waterline makes a great surface for such creatures to adhere. Once they do, they’ll be a drag both in terms of performance and esthetics.

It would be great if all you had to do was slap a couple coats of paint on the bottom and head off for your favorite cove, but there actually are quite a few variables to consider when it comes to choosing the right bottom paint for your boat. That means you are going to have to do some homework, ask questions at your local marine store, and double-check that any bottom paint you finally decide on will be compatible with the current coating over which it will be applied.

As a rule, you’ll want to avoid bargain brand paints and stick with the tried and true for this project. Interlux and Nautical paint, for example, are two companies that enjoy solid reputations at most full-service marinas. Both offer a variety of formulas from which to choose, have on-line support and Interlux also posts an anti-fouling paint compatibility chart on their website to make it easy to match a new bottom paint type with an older one.

Following are several key points to keep in mind as you get your bottom painting project underway. Even before suiting up and prepping your hull, however, be sure to check with your marina to make sure you’ll be allowed to paint your boat yourself. Some boatyards and marinas prohibit this act as a simple point of business; others may not allow it due to environmental concerns or regulations.

Safety First

Know this before you start: both anti-fouling bottom paint and sanded fiberglass are toxic. So, the very first thing you want to do is wear a respirator and protective eyewear, gloves and clothes when sanding (with a vacuum attachment to capture the sanding residue), scraping or painting. A tarp will be needed to capture the sanding residue and any paint chips (which will need to be disposed of properly.)  Next, make sure your vessel is firmly secured and perform a full hull check to ensure sure you won’t be painting over any damage that needs to be addressed.  Safety first is always rule number one.

Start With A Wash-down And Good Scrubbing

Before applying any bottom paint, you’ll want to power-spray below the water line to ensure as clean a hull as possible. This is best done when the boat is first removed from the water in the fall as most organisms are easier to wash away before they’ve had a chance to dry and set.

If you didn’t wash down last fall, you’ll still able to get the hull in prime condition before painting – but it’s going to take a lot more elbow grease. Plenty of scrubbing and a random rotary sander will be your best friends. Be sure the hull is dry before starting this task.

If the current bottom paint seems to be in good to fair shape, there’s no need to take it all off. Just scrape and sand any loose or flaky areas and recoat following the manufacturer’s directions on the can. If it’s in really bad shape, consider using a paint stripper formula or to have it professionally removed via media blasting to completely clean the hull before starting over.

Pick The Right Paint

It’s important to choose the right paint for the job at hand, says Matthew Anzardo, Marketing Manager for Interlux Paints. “That can take a little more research than you might expect since there are so many paint formulas available these days,” he says. “Take anti-fouling, for example. Some paints are designed to guard against hard fouling barnacles and zebra mussels while others are dual-purpose formulas that also guard against slime and algae.”

“There are also paints designed to last one year or multiple years, and some have specific restrictions,” continues Anzardo. “You shouldn’t, for example, paint over an aluminum hull with a copper-based paint. In that same vein of thought, you might need two different bottom paints to paint your hull and your stern drive if the stern drive is aluminum. There are also paints that simply don’t go over other paints; which is why it is important to check a compatibility chart.  (The Interlux Compatibility Chart can be found here:

Of course, most potential problems can be prevented by simply asking an expert at the shipyard or marine store where you purchase your paint for a little help. Actually reading the directions on the label is recommended, too, as you might discover some really important points such as how thickly to apply the paint, the overcoating and the launching times for the paint that you are using.

So, there is a lot to consider here – which is why so many boaters hire out the task to professionals. Still, you can negotiate these waters with a little bit of thought, research and a willingness to ask questions when you aren’t sure how to proceed. Just take your time, think it through, and get started as soon as the spring warms up because boating season is already knocking at the hatch.

Tom Schlichter

Tom is a full-time outdoors writer, editor and marketeer living on Long Island, NY. Follow him on Facebook at @outdoortomcorp or visit his website at

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