A boat tarp is a large sheet of strong, flexible, water resistant or waterproof material, used to protect boats from the weather and to cover them. It will keep out moisture, prevent mildew and mold and help rodents, birds and animals from getting in and damaging the boat. A tarp is usually made of cloths like canvas coated with plastic or latex or woven polyethylene.
The following are some common types of boat tarps:
Poly Tarp: It provides excellent protection from rain and heat, because it is treated with a weather resistant polyethylene coating. The material it is made of is high-density resin, with heavy-duty grommets. It is mildew proof, tear and acid resistant and can be used in subarctic temperatures.
Canvas Tarp: It is a good idea to use them for outdoor storage. They are hemmed and stitched all round and reinforced. The reinforcement is made of eyelets, which are composed of materials that will not rust easily. Canvas will last for years without allowing leakage. However, after years of use the tight weave of the canvas boat cover might loosen, allowing the elements through.
Some canvas tarps are more durable than others. Canvas boat covers last a long time because of their tight weave. Other materials can break down and deteriorate faster. You can also paint the canvas, much like an oil painting, giving it a little attitude and style. This will make it nice and attractive while protecting your boat.
Mesh tarp: It is also known as a shade screen. It is not as strong and durable as a poly tarp or a canvas tarp. It should only be used in light breeze environments.

Tarps are usually sold in pre-standardized shapes that would fit any kind of boat. They also come in many shapes, sizes and colors. You can also get a boat tarp customized for your boat. The proper customized boat tarps may be expensive, but they serve a good purpose of protecting your boat. Boat tarps are an excellent way to protect boats against every kind of weather. The tarp is used along with rope, which helps owners tie the tarp to their boat without any gaps, by putting the rope through the D hole.
Regularly search for rips, tears and signs of decay. Even if it is a minor damage, repair it as soon as possible. All marine supply stores sell repair kits and extra snaps so that damaged snaps can easily be repaired. It is important to determine if at some point you need to replace the tarp. Replacing the tarp will cost you much less than repairing a damaged boat. Tarps come in different kinds of fabric and they might have been treated in many different ways. The following are some guidelines to take care of your tarp, but be sure to read and follow the instructions that come with your particular product:
¥ Clean the tarp regularly, but never machine wash it.
¥ Use plenty of water and a soft bristled brush.
¥ Leave the tarp to dry naturally in a well ventilated environment.
¥ Fold it when it is completely dry. If there is trapped water in the tarp that could lead to the growth of mold or mildew, that might spread to your boat.
¥ If the tarp has a waterproof coating, it might need to be renewed every year or two. Always check with the manufacturer or dealer before buying waterproofing products, since not all of them might be suitable for your tarp.

HELPFUL HINTS:
¥ You should be able to tie the tarp down securely, so choose one that has high quality grommets that are rust resistant.
¥ Thoroughly dry all surfaces of the boat before putting a tarp on it.
¥ Use mildew control bags to cover seats and any other convenient surfaces of your boat.
¥ Never store the tarp aboard the boat. Always keep it in a warm, dry place.