Guide to Painting your Boat's Bottom

If you keep your boat in the water year-round, odds are that you might wonder what the bottom looks like and the condition of your running gear. Choosing the right bottom paint and coating goes a long way for the boat’s protection and performance, as well as your peace of mind.

To pick correct paints, several factors are considered such as the type of water, where you boat, how often you boat, the boat’s material and your budget. You don’t have to spend a fortune, but you should maintain it if you want to get the best performance.

Bottom paint is essential to protect the hull and prevent fouling of the bottom and running gear. Many choices are on the market today, and a smart boater will research the options when selecting paint to understand how the boat is used and where it goes.

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Which fits your boating style — hard or soft coating?

Hard paint coating does not wear away like an ablative (an older type of hull paint designed to come off slowly). It works all the time whether the boat is moving or not. However, with hard paints, the antifouling properties (biocides) leach out over time thus losing power to keep growth and barnacles from attaching. With ablatives, when you run your boat, the soft paint sloughs off exposing a new layer of antifouling and removing the old layer of growth. While boat movement is a big consideration for hard or ablative, many other factors are considered.

•Cruising Area: Especially in warm waters like the Caribbean, bays and sounds, you need a high- quality antifouling paint specifically designed for saltwater. These paints usually provide better protection against marine growth. Freshwater cruising doesn’t mean you don’t need bottom paint. Algae and other marine growth still foul the bottom and running gear based on temperatures.

•Hull Material: Hull material also plays a big role in paint selection. Most antifouling paints are suitable for fiberglass boats. Aluminum boats require antifouling paints formulated for aluminum surfaces to prevent corrosion and protect the bottom from marine growth and barnacles. Wooden boats may need specialized bottom paints designed to protect wood against fouling and rot. Some traditional copper-based paints work well for wooden boats.

•Environmental concerns: Be aware of local and regional regulations regarding bottom paint. Some areas have restrictions on certain types of bottom paints, especially those containing high levels of copper or other potentially harmful substances. Many boat yards are required to follow these regulations and won’t let you or the staff use paints that are locally restricted.

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Selecting the right paint

Once you know what characteristics you’re looking for, various reputable bottom paint brands are available, such as Interlux, Pettit, Sea Hawk and more. While it is important to consult with your boatyard or marina for recommendations based on local conditions, boaters should do their research. Most paint manufacturers have well-written instructions and guidance on use and proper application.

Be sure to follow manufacturers’ instructions for application, surface preparation, number of coats and drying times. Applying paint correctly is crucial for the paint’s effectiveness, and most poor paint jobs were doomed at the first step with surface preparation.

Some boaters use the same bottom paint on their running gear as the hull, but it’s not designed for this and will not last. Many options for paints and application methods are available, with potential solutions ranging from metal paints and zinc spray to brush-on paints. Some choose to go paint free on the running gear, and with frequent boat use and proper cleaning, this can be effective.

One coating gets a lot of attention. Propspeed’s bright and high-gloss gold appearance stands out in the boat yard and gets noticed by boaters who aren’t used to seeing it. Propspeed is a foul-release coating that is free of biocides and applied to the propellers, shafts, thrusters and other underwater metals. It creates a surface that is tough for marine organisms to adhere to instead of antifoulants. If you select this coating, make sure you understand the application process and your boat yard is properly trained to apply it.

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Regular maintenance is key

Maintaining your boat bottom well is crucial to get the life expectancy from a paint job. Inspect the bottom regularly, ideally once a month or before each outing. Look for signs of fouling, such as barnacles, algae or slime. If you notice fouling at the waterline, it’s also likely to be on the bottom. Use a soft brush or a pressure washer with a low setting to remove marine growth and slime where you can reach. Hire a diver to regularly clean below the water line. The warmer the water, the more often you need to do this.

Depending on the extent of fouling, you may need to haul the boat out of the water for a thorough cleaning or repainting. Hauling out should be a last resort, and if proper maintenance is done all year long, it isn’t always needed annually. When you do haul out, check anodes (zincs) for excessive wear and through-hulls for debris and growth.

Finally, keep records of when the bottom was last painted, what type and how much was used. This information is valuable for future maintenance and deciding on the next application. By staying proactive and following best practices, you can enjoy a clean and well-protected hull while extending the life of your bottom paint.