Any renovation project can be rigorous at best, and downright impossible at worst. Renovating a fibreglass boat is no different in that respect. If you start with a solid, good-condition hull, however, you'll find that the process goes a lot smoother than if you purchased or inherited a boat with a hull in poor condition. The interior plywood and soft surfaces are usually easily replaced, but a bad hull can break even the most well-intentioned renovator.
Clean the fibreglass hull using a speciality hull-cleaning chemical. These will remove water and rust marks on the gel coat of the boat, leaving behind the original finish. Most boat-cleaning systems are extremely labour-intensive, so plan for plenty of time to clean and restore the hull to its original condition.
Tear up the original marine carpeting from the deck of the boat. Even though the boat is fibreglass, the deck will be plywood. New marine carpeting is more like the carpet in your home and much more comfortable to walk barefoot on than marine carpeting from even ten years ago. To affix the new carpeting to the deck, use a marine-grade carpet glue, spreading the glue out over the entire deck.
Replace the original seat upholstery with new cushions and covers. Ultraviolet rays from the sun take a heavy toll on older vinyl upholstery, causing cracks and discolouration. Once the vinyl cracks, the foam in the seat is subject to mould infestation. If necessary, replacement seats for fibreglass boats can be ordered that simply bolt in place of the originals. While this makes the process more expensive, it also makes it much quicker.
Tune the engine and replace any parts that require replacement. If the engine hasn't been started in several years, it is likely that the gasoline in the tank has become fouled and will need to be flushed out of the system before attempting to crank the engine. While doing this, replace the fuel filter, air filter and spark plugs. With this complete, change the engine oil, then replace the boat battery. As long as the engine is in good condition, this should allow the motor to start when the tank is filled with fresh gasoline.
Clean the metal trim on the boat with metal polish and a rag, or if the trim has become pitted with rust, replace it. On fibreglass boats, the mooring cleats and rails are typically the most degraded parts, but you may find that the windshield frame is in poor condition as well. Contact the boat manufacturer for information about speciality replacement parts as needed.