The stages of hull deterioration are predictable. Mishaps and other docking accidents, scratches from dirt or salt, oxidation from UV rays, stains from mold and mildew, these all take their toll on the hull's luster. But with a little seasonal attention, the hull of your boat won't show its age, and that highly polished gelcoat finish can be sustained for years. Here are some tips on hull cleaning and maintenance that can be utilized within the context of your spring recommissioning:
If your boat has been kept covered during the off season, after the cover comes off, wash the entire hull with a strong stream from a hose to rinse away dust and cobwebs. Use a soft terrycloth rag, or a barman's rag, with plain dish detergent in warm water to wash grease, oil, and smeared dirt off the hull. Be careful not to let the soap dry on the surface before rinsing it thoroughly.
After drying, inspect the hull for any remaining stains, embedded dirt, or major dings. If the hull is relatively new and well kept, it should appear clean and fairly shiny. In this case, a coat of pure wax without cleaning compounds can be applied and burnished by hand or with a light-duty electric buffer.
Any remaining grease or tar will need a stronger cleaning agent. Every chandlery can sell you a bottle of boat soap. Most of these products contain some quantity of detergent, ammonia, bleach, or alcohol. Be careful if you attempt to mix your own concoction since some combinations of these ingredients become highly toxic. Really stubborn tar or oil may require a sparing wipe down with acetone to the local area.
Under no circumstances should you use an abrasive unless you are preparing to paint the hull. This includes household cleansers such as Ajax and Comet, and even mild scrubbing agents like Soft Scrub. Abrading the hull surface with these simply creates more porosity, thus setting in motion a cycle of ever-increasing need for abrasion. You can learn a lot about the condition of your hull simply by studying it. Stains from dirty water or mildew indicate that the gelcoat is becoming porous and is nearing the end of its life in an unpainted state. The moustache you see from the bow wave and sooty film at the exhaust can be removed in all but the most severe cases with a stain remover. Davis Fiberglass Stain Remover (FSR) is a favorite of cruising sailors.
Gouges or deep scratches in the hull will require that you repair them with new gelcoat. Now working with gelcoat takes some practice if you intend to to match the hull color, and you'll also have to learn the techniques of wet sanding and compounding the area until it is invisible. If you lack time, consider having a professional handle these tasks for you.
You can also judge the level of general oxidation by wetting a finger and running it across the dry surface of the hull. If it merely appears dull but does not rub off onto your finger, you can use a cleaner wax to finish your job. Because these waxes contain abrasive compounds, make sure that the one you choose is matched to the level of your oxidation They are available in a paste or near liquid form from 3M, Boatlife, Starbrite, and other companies for marine use. For gelcoat finishes I definitely recommend that you use a wax manufactured for a marine application, but cleaner waxes that have been manufactured for automobiles, such as Turtle Wax, do work well on painted surfaces.
If the gelcoat is oxidized to the point where chalky dust comes off on a wet finger, a major job of compounding is in order. Buffing compounds come in different strengths, or size of the grit, just like sandpaper. Again, be careful to select the right one for your particular needs. Use a large, soft, lambskin-buffing pad at medium to slow speeds. Do not apply much pressure, especially around transom corners or other hard radiuses. Once the dust and excess compound have been washed away, a complete wax job will keep the hull looking good for the season.
New proprietary restoration systems are available for boats that are on the last stages of the life of their gelcoat. Apple Polishing, Island Girl, and other systems use cleaners that pull dirt out of the pores of gelcoat and replace wax with special polymers that fill porosity and achieve a nearly new look. If your hull needs a total rehab, and you still don't want to repaint, investigate these products and see if any of them appeal to you.
There are some intermediate tricks involving partial coating that may help you delay a full paint job for a few years. By raising the bottom paint or widening the boottop you can hide severe staining along the waterline. This also protects those areas of the hull. Similarly, scratches from rubbing against docks or pilings just under the caprail can be masked with a larger cove or whale stripe.
Regardless of how much love is bestowed on the hull, the time will come when only paint will cure its ailments. The hull's surface will become so scratched and porous that only a coat of paint will beautify it. Painting a hull with new one or two-part paints is a major undertaking and can be accomplished by professionally applied spray or a dedicated amateur with brush and roller. But remember: once painted, the necessary care changes only slightly; the need to keep the hull clean and waxed remains the same.