Project 2: Preventive Maintenance

Antifouling and Blister Protection
Bottom painting may have a reputation as a tedious and messy job, but it is also one of the most important preventive maintenance tasks in keeping your boat performing in top condition. A clean bottom is safe, fast and efficient. Bottom growth reduces speed and maneuverability and increases fuel consumption.

There are many types of bottom paints (or antifouling paints) available and your choice will be primarily determined by
• What type of boating you do
• Where you boat
• What type of bottom paint has been applied to your boat in the past

Bottom paints reduce marine growth of barnacles, plants and algae by releasing toxic biocides at a controlled rate. The most popular biocides are copper compounds (cuprous oxide) and, generally speaking, the higher the copper content, the more effective the antifouling properties. Many of today’s high tech bottom paints also contain “slimacides” which act as a sort of sunscreen for your paint at the waterline.  By filtering out UV at the surface, algae and slime cannot form since the chemical prevents photosynthesis, thus boosting your antifouling protection. Look for slimacides on your favorite paints by their trade names of Biolux or Irgarol.

Primary Types of Antifouling Paints
Each type of antifouling paint has its own set of pros and cons. It’s important to choose the one that best fits your type of boating and works well in your area. You must also consider the compatibility with any existing bottom paint you will be painting over. Generally, softer paints can be applied over harder paints, but not vice-versa. There are exceptions, however, so it’s always best to consult a compatibility chart.

Modified Epoxies
Require yearly repainting if the boat is hauled out seasonally. Higher copper content will generally last longer in higher fouling areas like the Southeast and mid-Atlantic. These paints are generally the most compatible because they can be applied over almost all paints if the surface is properly sanded. Boosted antifouling paints are fortified with an additive that inhibits the growth of slime and algae.

Ablatives
Ablative paints wear away gradually like a bar of soap. Because of this gradual wearing away, stripping is not required. Multiseason ablatives may be hauled and launched repeatedly without having to repaint. This can be a huge time saver for those living in northern climates. Boosted antifouling paints are fortified with an additive that inhibits the growth of slime and algae.  Multiple-coat applications are required in the first year, but are well worth the cost and effort to eliminate 2 or 3 years of annual painting.

Thin Film Paints
Popular with racing sailors and go-fast powerboaters in fresh water. Dries to a hard, super slick finish almost instantly, allowing for a quick paint and relaunch. Must be applied by rolling with a solvent-resistant foam roller cover or by spraying with an airless sprayer.


Other Antifouling Paints

Soft or Sloughing Paints
Few paints can be applied over sloughing paints due to their very soft nature. Because modified epoxies have come down in price, sloughing paints are no longer an economical choice for most boaters.

Vinyl Paints
Special racing paint. The least compatible because they contain extremely aggressive solvents and cannot be applied over any other type of paint except another vinyl paint. Even then, it’s difficult to get a good bond without a very thorough sanding.

Choosing the Right Paint
Having trouble selecting the optimum Bottom Paint for your boat? We can help. We stock a vast array of Bottom Paints for pretty much every type of hull, water and climate. Whether you’re a trailer boater, sailor or cruising powerboater, we can help you quickly and easily determine the best Bottom Paint to fit your boating needs. Just stop by your local West Marine or BoatU.S. store and speak to an associate. You can also call 1-800-BOATING or visit our Web site, westmarine.com, for product advice.

Gelcoat Blistering & Applying A Barrier Coat

Gelcoat Blistering
If your boat has blisters, they should be fixed now or the problem will only worsen. If your boat does not currently show any signs of blistering, it’s a good idea to consider applying a barrier coat to prevent any potential problems in the future.

Blistering occurs as water is absorbed by the hull throughout the season and causes the gelcoat to delaminate from the fiberglass. Blisters can come in many sizes, but usually look as though your hull has a case of chicken pox. They occur more frequently in warmer climates where boats are likely to be in the water for longer stretches of time, however, they can plague boaters everywhere.

Blisters can occur on boats of any age, at any time. If your boat develops blisters, there is a multistep process involved to fix them. Interlux has a blister repair guide to help with the process. Of course, the best way to deal with blisters is to prevent them from occurring in the first place. Barrier coats are designed to do just that. By providing an impermeable layer of epoxy between the paint and the hull, water cannot be absorbed and therefore, blisters do not form.

Applying a Barrier Coat
• Start with a clean hull. This means: “to bare gelcoat” clean. All remnants of old paint must be removed to get a good bond with the fiberglass.
• If you have an older boat with existing bottom paint, the old paint must be sanded or “stripped” off.
• If the barrier coat is to be applied on a new hull, prep the surface by cleaning the hull of mold release agents with a solvent wash.
• Next, lightly sand the surface with 80-grit sandpaper and you’re ready to apply the barrier coat per manufacturer’s instructions.

Fast Fact
When applying a multiseason ablative, apply the base coat in a contrasting color to all of the following coats. This allows you to visibly see when the paint has worn away to the base coat and is in need of repainting. Ablatives are compatible with most paints by simply sanding the old coat and applying.

Safety First!
Bottom paint is toxic and, when painting your boat’s bottom, much of the work is done directly above your head. Avoid breathing in fumes or getting paint or other chemicals on your skin or in your eyes.

Protect yourself with
• Disposable gloves
• Dual filter respirators
• Coveralls
• Head socks
• Eye protection

Set up your work area so that sanding residue or paint will not escape into the environment. Wash up and thoroughly clean your work site when finished.

Basic Preparation
• Painting over a barrier coat: If you decided to tackle the barrier coat project, a light sanding with 120-grit sandpaper after the final coat is all that is necessary to prep the boat for paint.
• Painting a new boat’s bottom: If you are painting a new boat for the first time, you must wipe down the entire bottom with a good solvent wash to get rid of all mold release agent from the factory. You can then either lightly sand the hull with 120-grit sandpaper or use no-sand primer.
• Painting over existing antifouling paint: Powerwashing will remove any remaining dirt or light fouling. For heavier fouling, use a strong acid-based bottom cleaner. Be sure to wear eye protection, a good respirator and rubber gloves as this type of cleaner if very caustic.
• Lay out a larger tarp or drop cloth to cover the entire work area. Once the bottom’s surface is thoroughly dried, you are ready to sand. Sanding is necessary to give the old surface some “tooth” to hold the fresh paint.



Bottom paints are toxic by nature, and most are solvent based. Always try to cover exposed skin and eyes, and wear a respirator to avoid breathing any toxic fumes. Use a disposable coverall suit, gloves, goggles and a high quality respirator.

• Knock off any loose paint with a scraper, then using either a sanding block or a dustless DA sander lightly sand the entire bottom with 80-grit sandpaper. Make sure to spend a little extra time on high or uneven areas. You want as smooth a surface as possible to minimize drag. When you have finished sanding, wipe down the surface with a tack cloth or rag.
• Select a masking tape that’s right for job. Some things to keep in mind when selecting tape:
    o General-purpose tapes are only designed to be left on a surface for 24 hours or less.
    o Long-mask tape is a much better option when bottom painting, especially when applying multiple coats



• Tape as close to the existing bootstripe as possible. Start from a natural breakpoint in the line and draw the tape every one-and-a-half to two feet for a smooth, even line. Also, tape around transducers, prop shaft struts, thru-hulls or any other metals as the copper in the paint will react with other metals, causing galvanic corrosion.

Applying Bottom Paint
• For most bottom paint applications, rolling works best. A 3/8” nap solvent-resistant roller cover is the ideal match for most bottom paints. One exception is the thin film paints that work best either rolled with a solvent resistant foam roller cover or sprayed with an airless sprayer. Make sure to get a few sizes of chip brushes to cut in around the masked areas and at the waterline.
• After thoroughly stirring the paint, pour it into the paint tray and begin rolling the paint evenly from one end of the boat to the other.
• Recoating should be done following manufacturer recommendations. Times can vary based on paint type and temperature. Most also have a required drying time prior to launch, so be sure to factor that into the equation as well.
• Once the paint has dried, remove all masking tape and clean up the area.
• Be sure to properly dispose of the old paint and any solvents used for clean up.
• If your boat is on jackstands or a cradle, painting under pads can be tricky. Depending on the drying time for the paint, you may be able to paint under the pads or bunks when the boat is slung for launch. Check with your yard. Some paints will dry adequately in the short time it’s “in the air.”

To determine bottom paint quantity, estimate the approximate surface area of the hull below the waterline using the following formula:

Project 4: Regulatory Checkup