You only need to clean the bottom of the boat beneath the waterline. This is the keel of the boat. Look for the boot stripe, which is an unpainted border between the bottom paint and the topsides of the boat (which are the sides of the boat above the waterline). To remove stubborn or hardened grime, use a power washer. You can rent one at a hardware store. A boatyard may also have one on hand that you can borrow or rent.
If you are stripping the paint, place a tarp underneath the boat to pick up the debris. Only strip paint beneath the waterline of the boat. Do not scrape paint from the topsides of the boat. If you keep your boat at a boatyard, ask the management if anyone there can use a power blaster on the boat. This tool should only be handled by professionals, but it can strip the paint much faster than doing it by hand. Ask for soda blasting on a fiberglass boat or sand blasting on an aluminum or steel boat.
You can buy a good boat primer at a marine supply store or online.
Ablative paint is good for slower boats that are in constant use, such as fishing boats or pontoon boats. Ablative paint wears away on its own, which prevents you from having to remove the paint later on. Hard bottom paint is ideal for fast boats or boats that may not be used as often, such as speed boats. These paints don’t wear away very easily, but it is more difficult to remove them when you need to apply a new coating. There are “hybrid” or “semi-hard” paints that combine the benefits of ablative paint and hard paint. These are good for powerboats or frequently used boats.
Do not paint above the waterline. The topsides of the boat require a different type of paint than the bottom. If you need to add more paint to the tray, make sure to stir it in the can first.
Some brands of paint may recommend that you do 3-4 coats total. If you do this, just remember to sand the keel in between each one. If you want, the top coat can be a different color than the bottom coats. This will help you realize when the paint is wearing thin. [13] X Research source
If you used ablative paint, bring the boat up out of the water. Use a hose to spray away any grime and scrub off stains with a sponge. You do not need to use soap. If you used hard bottom or hybrid paint, you can dive down below the water. Use your hand or a rag to wipe away any grime or algae. You can also hire a diver to clean the boat for you.
If you’re unsure what type of paint was used before on the keel, take a wet rag. Wipe the rag along the existing paint. If the paint wipes off, it is an ablative paint. If not, it is a hard or hybrid paint.
