How do you paint a boat so it looks stunning and lasts? Boat painting is an important task, a good paint system can turn a boat that’s starting to look a little tired back into one that turns heads. However, whatever the size of the boat or yacht you are painting, the job must be done properly. Cutting corners when choosing paint, preparing the surface, or in the application all too frequently creates problems that are time consuming and expensive to solve.
How to paint a boat: key principles
The overwhelming majority of new boats are not painted above the waterline – instead the surface finish is the outer layer of gel coat. However, with the passage of time many acquire a number of coats of paint, either to satisfy an owner’s wish for a different colour scheme, or to cover up the inevitable knocks and scrapes that accumulate as the boat ages.
Of the yachts that do have paint finishes applied from new, most are larger vessels, or high-budget racing yachts, whose owners have invested in a top of the range coating such as Awlgrip that must be applied professionally. This creates an outstanding high-gloss and exceptionally hard coating that’s even better than gelcoat at resisting scuffs and knocks. On the downside, these advantages come at an eye-watering price in terms of material and labour costs.
The point at which the hull of a boat is first painted is often when the gelcoat loses its shine, and a simple polish won't restore the original gloss. This is especially true of dark colours that fade quickly in ultra-violet sunlight. However, many boats are painted prematurely – in many cases, even on 25-year-old boats, the topsides can be brought back to an as-new appearance if the surface is cut back more aggressively, by sanding with very fine abrasive paper of around 640 grit, then moving to 800 and 1200 grit before applying the polish. However, there will come a point in a boat’s life at which the condition of the gelcoat is such that further polishing is no longer a viable option.
Preparation for painting a boat
The old adage that says that most of the work in achieving a perfect paint finish is in the preparation remains as true as ever. Any surface damage must be filled and sanded until it’s absolutely smooth. This is generally an iterative process, with each application of filler, and subsequent sanding resulting in a slightly better result.
Similarly, any previous coatings must be strongly adhered to the substrate and sanded so that they are fair, with no brush marks or other flaws that will show through in the final finish. Any changes in the thickness of the remaining paint should also be feathered to as smooth a transition as possible.
The next stage is to apply a high-build primer that will reveal any remaining small imperfections, allowing them to be sanded out. The final preparations before painting are to sand with medium grit abrasive paper to provide a good mechanical key that the new paint will readily adhere to, following by cleaning and degreasing the surface with a rag soaked in methylated spirits. See How to prepare a boat for painting.
Removing old paint layers
Paint systems that are in a really poor condition are usually best removed in their entirety before the boat is repainted, so that there’s no risk of applying new paint to material that is not well adhered to the hull. Unfortunately, most conventional paint strippers are not suitable for use on fibreglass boats – they will attack both the gelcoat and the underlying structure just as effectively as the paint system. While a product such as International Paint’s Interstrip solves this problem, mechanical sanding (allied to appropriate dust control measures) remains the most common means of removing old marine paint on fibreglass vessels.
However, it’s next to impossible to abrade many non-slip deck coatings. This is no problem if the existing coating is in good condition, as areas can simply be thoroughly cleaned and degreased before applying additional coats. However, if the existing paint is poorly adhered to the boat it will need to be removed. The safe way of doing this is with a suitable stripper, although some professional operators will use a heat gun, with extreme caution to ensure there’s no damage to the underlying gel coat and laminate.
How many coats of paint?
The number of coats of paint that needs to be applied varies with a number of factors, especially if the new paint is of a markedly different colour to the original. For perfectionists seeking the best finish, the boat should look almost perfect after application of the undercoat. To get to this stage from scratch, it may require two coats of primer, followed by three of undercoat, and then two or three topcoats. However, if the aim is to simply refresh the finish of an existing and largely sound paint system, two additional topcoats may well be all that’s needed.
When spray painting a boat, each coat is very thin compared to applying paint with a brush or roller, so many more coats are required. However a sprayed coat dries extremely quickly, allowing a large number of the thin coats to be applied in a given time frame.
Yacht paint application methods
The first choice of professionals by a large margin is spray painting. However, this has a number of disadvantages for most do it yourself boat owners. In the UK it’s best done undercover and requires a high degree of expertise to avoid runs and sags. In addition other nearby vessels (and even cars) will need to be fully protected with dust sheets to prevent overspray.
A better approach for an amateur application is to work as a team of two people, with one applying the paint with a small roller, and the second person using light vertical strokes with a wide brush to “tip off” the brush marks, leaving a smooth surface. Although more labour intensive, if subsequently polished, this process comes close to rivalling the finish of a spray-painted boat, but with none of the drawbacks.
Find out more about preparing, choosing and applying marine paint in our feature How to finish your topsides: paint, polish or vinyl wraps.
Painting decks, coachroofs and cockpits
The process of preparation is very similar to that for the topsides, although a lot more time needs to be allowed due to the many small areas that can't be attacked with a big sander. Similarly, don't under-estimate the tie need to apply masking tape around fittings, windows and other obstacles.
It's also worth bearing in mind that there are few modern boats that will look good with non-slip paint covering the entire deck and coachroof. While planning the work it's therefore worth taking time out at an early stage to figure out what type of paint is most appropriate for each part of the deck and superstructure.
While many parts of the deck will have sufficient space for a roller to be used, as described above, small and fiddly areas are best painted with a brush. Again, don't skimp on quality here – a decent brush will produce a better finish in less time.
How to varnish a boat
A beautifully varnished yacht will always look great, but it’s an appearance that invariably comes at the price of a great deal of time. Surface preparation is even more important here than with painting the topsides or deck, as any imperfections will show more clearly in the final finish. Varnish is also more prone to damage by frost and sunlight than paint finishes, and more coats are often required than for regular paint systems.
To get the smoothest possible final finish, varnish is best applied with a brush in a three-stage process. First, apply the liquid in working in along the grain of the wood, then spread it out using brush strokes at 90 degrees. Finally, erase the brush marks using very light strokes in the direction of the grain.
Read our expert tips on how to obtain and keep a perfectly varnished finish in our feature 8 ways to maintain flawless varnish coatings.
Interior boat painting
While the overwhelming majority of interior woodwork is varnished, a variety of finishes other finishes including lacquer and oil may be used on interior woodwork, particularly if it's of a durable species such as teak.
In most cases, interior woodwork will only need attention in specific areas that have been affective by water damage, exposure to sunlight, or deep scratches. Although these defects are all liable to change the colour of the surface of the timber, a complete removal of the entire coating system is rarely needed. Instead, the damaged area can usually be colour-matched to a shade that's very similar to the surrounding timber.
This can be done either with the use of bleaches to lighten an area that has, for instance, become darkened through water damage (after thoroughly drying it out), or with the use of wood dyes to darken the timber. In some cases, all that's required is application of strong tea – you can experiment with different strengths to get exactly the right shade.
Cabin sole boards require a durable finish that will resist the abrasion of many pairs of shoes and sea boots. A high-gloss finish here is often not ideal, as it can prove slippery in a seaway, which makes satin a better choice. Don't be tempted to economise by using domestic floor paint, as most types are water-based and will not cope well with a sustained period of very damp conditions.
Antifouling a boat
Something that no owner of any boat that is kept afloat can escape is the need to antifoul the bottom of the hull, along with keel and rudder, to slow the growth of marine organisms. There are a bewildering number of different types of antifoul on offer, all formulated to suit different types of boat, usage, location and the depth of the owners’ pockets. Find out more with our guide How to choose antifouling paint.
It’s important to remember that all types of antifouling are toxic products, so a high level of personal protection is required and the hull should not be dry-sanded below the waterline. If the hull was properly cleaned with a pressure washer on being lifted from the water, little additional preparation is generally needed beyond checking for any loose or flaking paint, providing the new antifouling is of the same type as previous coats.
However, if many layers of antifouling have built up over a number of years there will invariably be some areas that are not well adhered to the hull and therefore need to be removed. While a product such as Interstrip can be used for DIY removal, although the best method by far is soda blasting. A professional specialist can carry this out in a single day, even on a large yacht, leaving a substrate that’s ready for priming. In most cases the cost of this is hugely preferable to the DIY alternative that may take several weekends of back-breaking work.
Generally at least two coats of antifouling are needed to provide a reasonable level of protection, although in areas of heavy fouling a third will help keep the bottom clean for longer. Antifouling is best applied with a roller at the end of a long extension handle, as this will minimise the amount of bending, stooping and reaching upwards you have to do. The long handle will also keep you as far as possible at arm’s length from the noxious paint.
Read more about preparing and applying antifouling in our feature How to prepare and apply antifouling.
Looking after marine paint systems
A little regular maintenance can significantly reduce the total time needed to maintain a paint finish in good condition. In particular, deal with knocks and chips as quickly as possible and certainly before winter, when any water that finds its way under loose paint will cause greater problems when it freezes.
A handy tip is to keep a small match pot, of the type used for household paints, filled with the appropriate paint for your boat. These come with a brush built in to the lid, so any small areas of damage can be sealed immediately.
Painting wooden boats
These deserve special consideration, as the paint is essential in maintaining the integrity of the boat’s structure by keeping moisture (especially rain water) out of the timber. However, traditionally build wooden craft also have a great deal more movement, both in terms of expansion and contraction and movement between planks, than more modern craft. The result is that the paint must also flex – if it does not then it will crack prematurely, allowing water to reach the timber.
This points to the relatively soft and flexible single pot types of paint as being best for wooden craft. The exception to this is plywood vessels, or those made from strip planking, where there’s no movement between adjacent planks.
If you own a wooden boat never procrastinate on giving the paint system attention as soon as you notice the beginnings of a problem – the longer you leave it the bigger the eventual repair will be. Don't worry unduly if your initial touching up doesn't look cosmetically perfect – it's still likely to be neater than the boat will look a few weeks later after water has penetrated underneath the paint system and into the timber.
For more boat maintenance tips, see Boat maintenance: how to look after your boat and 15 best boat fitting out tips.