When I see a boat with well maintained exterior woodwork it certainly draws my attention; and it suggests to me that the rest of the boat is well maintained too. Increasingly rare are boats with a lot of highly varnished woodwork, know as 'bright-work'. I happen to have one and maintaining that finish is one of my passions.
I get a great deal of enjoyment from my boat, and maintaining her cosmetic appearance adds to the pleasure. For me, aesthetics count. If you own a boat with exterior woodwork in poor condition then deciding how to restore and maintain it may seem daunting. In my view, there is no excuse for allowing the modest amount of wood trim on most modern boats to remain neglected: what I call the 'barn-board' effect. There are easy- to-use products that will beautify and protect the wood with a minimum of effort. On the other hand, if you have a boat with a lot of woodwork, and both a limited amount of time to work on it and a limited budget with which to have someone else do it for you, it may be necessary to be selective and limit the size of the restoration project.
Stand back and observe your boat and the wood trim or structure that you see. Perhaps it is a toe-rail that highlights her shear-line or the teak 'eye-brow' that follows the length of the deck-house and helps to make it appear lower than it is. Every boat will be different with respect to the woodwork that is essential to its' over-all appearance. Your refinishing and maintenance project should start there.
Developing a refinishing plan will also require you to examine the woodwork closely to see if it is properly bedded; and whether there are joints in the woodwork that are allowing water to access end-grains, darkening it. It is a waste of time to refinish wood that will not hold a coating because of water penetration. The species of wood used on your boat must also be determined. Different woods require different finishes and primers. Sometimes woodwork may need to be replaced if its' condition or installation is poor. If you think that you have such a problem, seek some good professional advice.
If the woodwork in question is in good condition and properly bedded, then you can decide how to proceed. Often teak is very course and grainy due to the use of chemical cleaners. They eat-away, with the aid of scrub-brushes, at the soft fibres leaving the harder gain in place. In this instance, sanding is the usual first step.
If there are remnants of a previous finish on the wood then removing it by some means prior to sanding may be advisable. Both the product you are trying to remove and the potential for damage of any surrounding fibreglass or painted surfaces will all have to be considered. Don't hesitate to seek out knowledgeable advice before commencing with the job as the wrong steps can cause damage that will greatly add to your work. I have used scrapers and both chemical and heat-gun type strippers. Sanding is tedious but, carefully done, it minimizes the potential of collateral damage. Power-sanders only save work in certain circumstances. Keep in mind the damage that they can do. Their use should be carefully considered. Hand sanding is usually the best alternative.
Sand your wood with the grain. Take care to distinguish between veneers and solid wood. Don't be too aggressive with the sanding of veneer surfaces. It is easy to sand-away the layer that one is trying to restore. On the other hand, if I am working on a substantial rail-cap or toe-rail of solid wood that is water stained or has remnants of an old finish, I may start with #60 or #80 grit garnet sand-paper. I mask adjacent surfaces so that I do not score them at the same time. I almost always sand a surface twice with a given grade of paper before moving to a finer one. Exactly how much sanding is required and with which grade of paper to begin is something that one learns with experience. It will depend on the smoothness and condition of the wood at the outset. Starting with #80 grit (when warranted), I complete the job with #220 (never any finer) and I use three intermediate grits in between. This probably sounds like a lot of work and it is; but good refinishing jobs are 90% preparation and 10% application. Once you start applying your coating of choice, you are committed. You can't go back and sand-out the scratches that you missed.
Choosing the right coating for your woodwork is a matter worthy of careful consideration. Most chandlers can be of help and have access to the detailed instructions of the manufacturers. A number of factors will enter into the decision: the cost and availability of the product; its' track-record for longevity; its' ease of application given your circumstances; your application skill-level; the wear that the finish will experience; the type of wood being finished; the type of finish that you desire: high-gloss or matte; and the time and effort you have available for the job.
So what products should you use? A popular alternative for those wishing to both protect their wood and obtain a reasonable looking finish with a minimum of effort is Cetol M made by Sikkens. It is easy to apply. It's reasonably long lived. It seems to adhere well and it is not prone to peeling. It does not require a primer, it contains colorant such that it evens-out the color of the bare wood and it is forgiving of touch-ups. The down-side is that it produces a matte finish that is not very abrasion resistant. There is now, however, an optional, second-part gloss finish which must detract from the simplicity of maintenance of the original. Additionally, after a couple of coats of Cetol, the wood-grain is lost due to the colorant and the solids in the product that produce a 'muddy' effect that I dislike.
For a clear, high-gloss finish I prefer varnish. The decision to varnish does require a certain commitment to on-going maintenance, however. It also demands a level of preparation that is greater than that required by Cetol. The maker of the varnish that I use recommends a sealer for teak, due to its oily nature, that is applied before the varnish. Mahogany's rich, dark colour tends to fade quickly so a stain or a paste wood-filler is recommended before varnishing. The first coat should be thinned heavily to encourage penetration. Varnish also requires a minimum number of coats to build-up the finish so that it will handle some abrasion and acquire its' designed UV resistance. In my experience, four or five coats constitute the minimum 'base'; but this can be attained over the course of the first season. I use a marine-grade of phenolic resin/ tung-oil based varnish with extra UV filters by Pettit called 'Flagship'. It is best applied early on a not too warm day with no wind. When it is done correctly, it provides a glass-like finish that needs recoating only once a year after the base is attained.
Much has been written on the subject of varnishing techniques. Proper, dust-free, surface preparation including a wipe-down with an appropriate thinner, masking to speed cutting-in, good, clean bristle (not foam) brushes, properly thinned (fresh) varnish and careful but quick application are a few of the 'secrets'.
If you have a lot of woodwork, it is important to realize that you will probably use different products and finishes in different places. Don't dismiss the idea of reducing your work-load by painting certain parts of your woodwork. Well-executed paint-work of a complimentary colour can look very good indeed; and it is lower maintenance and more durable than clear coatings. If you love varnish but simply cannot manage to apply it to everything you would like to do, then varnish the showy parts that will hold it well and use Cetol or paint on the rest.
There are plenty of other brands and products available. I favour ones that can be obtained locally and have a good track record for longevity. I avoid epoxy and other two-part coatings due to the difficulty of stripping them when the time comes. Eventually it will be necessary to strip-off a finish or 'wood' it, and start again no matter what the level of care and the claims of the manufacturer. I 'wood' my bright-work every 10 to 12 years. I think that this is a very respectable amount of time for a finish to last. I do it on a rotation so that I am only tackling one section at a time.
The results of your refinishing efforts will enhance the appearance and value of your boat. As a bonus, your work may cause you to look back at her admiringly more than ever.