10 Steps To The Perfect Topside Paint Job

By Roger Marshall

Don't gloss over the facts. If your boat is past its prime, it might be time to consider a paint job.

Shiny boat hull finishA smooth, shiny finish after painting your hull is the result of careful preparation.

Your home is your most-valued asset, so you keep it painted and looking nice. Your boat is probably your second most-valued asset, but how often do you paint it? For most boat owners the answer is — never! It's often seen as too expensive, or you might mistakenly think that fiberglass is a maintenance-free material.

Rub your boat's hull with your finger. If it comes away with a chalk-like residue, the gelcoat is oxidized and in need of restoration. In some cases, the shine can be restored by compounding and polishing, but if it's too far gone, painting is the answer. When done correctly, a good paint job will last for many years, but it does take some care, dedication, and a fair chunk of time to do it well. So how do you paint your hull? Ask any painter, and you'll learn that 90 percent of the work is preparation. Applying the paint itself is the easy part. And with today's paints, there's no reason why you can't produce a good job on your own.

10 Steps To A Perfect Hull

1. Carefully measure around your hull from the sheerline (the top of the hull) to the bootstripe. Note this measurement, as you will need it later. Now carefully wash down your hull using soap and water and a scouring pad. This removes potential contaminants, such as wax and polish, that might show up later and mar the finish.

2. If the gelcoat on the hull is severely oxidized and has a chalky look to it, the oxidized outer layer will have to be removed. Use a random-orbit sander or longboard with 120- to 180-grit sandpaper. But DO NOT sand off the entire gelcoat. If you remove the gelcoat, you will have to reapply it and spend at least another week refairing it.

If the oxidization is minor, the boat has already been painted once or twice, or the hull has rust or exhaust stains on it, use 220- to 300-grit sandpaper on a random-orbit sander or longboard.

3. If you've used a random-orbit sander, stretch a thin batten (measuring 3/4 inches by 3/4 inches by 10 or 12 feet) along the hull and look for hollows and dips. These should be filled before proceeding using Interlux Interfair, AwlGrip AwlFair, EMC2 QuantumFC, or a filler compatible with the paint you will be using.

4. Sand smooth any filled patches, and check the hull fairness with your batten. Repeat until your hull is perfectly fair, then sand with a longboard using 320- to 400-grit to get a perfectly fair finish. Finally, thoroughly clean the hull so it is completely free of dust and ready to receive paint.

Masking off a Seacraft boat for paintingMasking off is critical to save getting paint on rubrails and other parts. Use proper masking tape, not the inexpensive variety that leaves behind a sticky residue. (Photo: Roger Marshall)

5. Apply an undercoat. The undercoat should be compatible with the topsides paint you intend to use. You can roll and tip or brush the undercoat onto the hull. Many painters use an undercoat that is the same color as the topcoat. This is especially important if you are changing from a dark-colored to a light-colored hull or the other way around.

6. After applying the undercoat, let it dry according to the manufacturer's recommendations, then sand again with 300- to 400-grit. Check the smoothness of the hull with your batten. You may need to apply a second undercoat if you have heavily sanded any area of the hull.

7. After the hull is completely smooth, wipe it down with a solvent to remove any grease or oil, including the oil from your fingerprints. Nothing is worse than finding a perfectly finished hull with the whorls of a fingerprint embedded in it.

Roll and tip method of paintingThe roll-and-tip method, shown here on a dinghy, can achieve results close to that of a sprayed finish. (Photo: Mark Corke)

8. Only when the hull is perfectly smooth and fair should you think about applying paint. Apply topsides paint by rolling and tipping (see "Applying Paint"), brushing, or spraying. If you spray, mask off all parts of your boat that you do not want to get overspray on. This means everything, including the underbody, the props and rudder, topside, and deck. You will be surprised how far overspray can go. Comply with all environmental regulations; for instance, use drop cloths, and tent when spraying. If you brush-paint the hull or roll-and-tip it, simply mask off the rail and any woodwork above the sheerline. You may also want to mask off the boottop, the line that separates the glossy sides from the antifouling.

9. When you paint, be it spray or brush, wet the area around your boat to keep dust down. Also ensure that the temperature is between 55 F and 75 F and that humidity is below 80 percent. Although it's possible to paint your boat outdoors, you will get far better results if you can move it indoors. Also consider the dew point because most paints require that the temperature be at least 5 degrees above the dew point at all times during the application and drying process.

10. Keep in mind that you may have to give the topsides two or three coats of paint, so don't mix too much paint at once. After painting, let the hull dry in a warm area for at least 24 hours — and, preferably, for two or three days to be sure that it has hardened. A full cure takes up to three weeks for most paints, although Quantum's paint is fully cured in one week. Follow the manufacturer's instructions for all steps.

Choose The Right Paint

One-part, two-part, polyurethane, enamel, or alkyd paint: Which is the best one to use? One-part paints can be enamel or polyurethane, but they tend to be slightly softer than two-part polyurethanes, and, I am told, their gloss does not last quite as long. Enamels tend to have less gloss and are more brittle than polyurethanes.

What is probably the most well-known topsides paint, Awlgrip, is only available to professionals. But Interlux's topsides paints, the two-part Perfection or the one-part Brightside, are available to DIYers. Pettit's one-part Easypoxy and two-part EZpoxy are also available to DIYers. Epifanes also makes a two-part polyurethane topsides paint.

A relatively new paint on the market aimed at DIYers is made by Engineered Marine Coatings. The company makes a Genius Bucket. This 5-gallon pail contains everything you need to paint a smaller boat: latex brushes, gloves, masking tape, scour pads, mixing cups, rollers and handles, 2 quarts of base, 2 quarts of brush activator, 1 quart of reducer, and 1 quart of paint in the desired color — all for $499.99. If you don't see the color you want, you can ask the company to mix it. Note that the kit doesn't necessarily include all materials you'll need for prep.

Applying Paint

To roll and tip, first dip the roller in the paint and roll it onto the hull. Try not to put too much paint on the roller; otherwise, you may get runs. Roll fore and aft and then up and down to ensure the best coverage. Use the tip or end of a dry fine-hair brush to tip the paint smooth. Work fore and aft, then up and down to get a very smooth finish. Work on only a small area at a time — no more than a square yard — then move to the next area. Keep a wet edge at all times and work from the wet edge into the dry area.

To brush paint, use a marine paint-grade sponge brush and apply a brushload at a time. Again, work only in a small area before moving on to the next.

To spray the paint, thin it to the manufacturer's specifications and spray in a fore-and-aft pattern. Make sure you lift the spray gun off the job before stopping your spray stroke.

Sanding

Sanding is not difficult, but you need to be careful. For a severely oxidized gelcoat or a larger boat, using a random-orbit sander will speed things along and make the job a little less tiring. But you must be careful to hold the sander exactly parallel to the hull or you'll get swirl marks or gouges. Deep swirl marks are extremely difficult to remove.

When using a random-orbit sander, I attach a shop vacuum to the sander to suck away the sanding residue and help to keep the job and myself clean. Most marinas require this; if you don't have one, many will rent you a vacuum sander.

To avoid swirl marks, many builders use a manual longboard sander and work back and forth horizontally. (A longboard uses a strip of sandpaper between 4 and 8 inches wide, and the board can be any length from 24 inches for one-person use to a two-man, 6-foot-long board.)

Safety Precautions

Many topsides paints contain isocyanates that are dangerous if inhaled. Therefore, the operator should wear a respirator with new filters for each spray job. Isocyanates filters degrade over time and should be used for no longer than 30 days. The best painters wear a hooded Tyvek suit taped at the wrists and ankles to prevent overspray from getting inside the suit. Rubber gloves, safety glasses, and Tyvek booties complete the ensemble and should cover your entire face and body.

Isocyanates are not so prevalent when paint is brushed or rolled, but a respirator is still a good idea. A Tyvek suit helps to protect clothes, and rubber gloves will prevent having to use a solvent to remove paint from your hands and fingers. When sanding, at a minimum use a sanding mask with two elastic straps.

A respirator is better. 

Roger Marshall is a writer and yacht designer who lives in Rhode Island.

— Published: April/May 2017


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