Aluminium is perhaps the perfect material for building boats, especially flat-bottom fishing and hunting boats. Aluminium is lightweight, durable and easy to work with. But like most metals, it can be difficult to paint. The trick to painting aluminium lies in the preparation. A clean surface and proper materials are key.
Balance the aluminium boat on the two sawhorses. Getting the boat up allows you to work all the way around the boat much better than you could if it were on the ground. The initial positioning of the boat on the sawhorses isn't important, although it may be easier if the bottom of the boat is on the sawhorses, with the inside area of the boat facing up.
Sand the boat completely. This step is necessary only if you're repainting an aluminium boat that had a previous coat of paint. You could do this with a block of wood and a sheet of regular sandpaper, but the most efficient method is to use a hand-held electric sander. Sand the entire surface of the boat, inside and out. Don't be concerned if you can't get 100 per cent of the paint off. And don't worry about scratching the metal with the sander, because these scratches will be invisible later and actually provide more surface area for the paint to stick to. You might find it easier to sand the inside of the boat first, then turn the boat over on the sawhorses to sand the outside.
Wash the boat. Fill your bucket with soapy water, and use a brush with stiff bristles to scrub the boat down. Scrub the boat as hard as possible to remove any debris caused by the sanding. Rinse the boat with a water hose, preferably one with a power spray nozzle. Allow the boat to dry completely.
Roll out paper or plastic on the floor of your work area. Anything that may be damaged by paint should be removed from the immediate area, and other items should be covered by paper or plastic. Open any available windows, and use electric fans to provide ventilation.
Apply primer to the boat. For best results, use an oil-based primer made for use on metal. Many professional painters recommend thinning the primer so that it can more easily work its way into the microscopic scratches on the boat. You can thin the primer by mixing a pint of paint thinner into a gallon of primer. You can use brushes or rollers, but you will get a cleaner, more even coat if you use a paint sprayer to apply the primer. Start by spraying the primer on the inside of the boat, allowing it to dry, then turning the boat over to apply primer to the outside. Allow the primer several hours of drying time before you begin painting.
Paint the aluminium boat the colour of your choice using a water-resistant paint. Again, it will be much easier to first paint half the boat, allow it to dry, then turn the boat over to paint the other half. You may need to apply two coats to get the desired colour. Allow the paint to dry completely.
Apply a clear coat. The clear coat is just sprayed onto the boat in the same manner as the primer and paint. The clear coat will provide protection against the elements and against scratching, and it will give the boat that newly painted look. But it will also make the boat look somewhat shiny, so you may wish to skip this step if you'll be using the boat for hunting. Should you decide not to apply the clear coat, you'll need to paint the boat much more often.
To prevent paint runs, apply paint in thin coats, using a broad sweeping motion.