Antifouling bottom paint is needed if you store your boat in the water. If left in the water without protection, marine growth may attach to your boat’s exposed hull. Marine growth slows a boat down and increases fuel consumption. Here are the items that you will need in addition to the bottom paint for the proper anti-fouling bottom paint application.
• 60–100 grit – Suitable for the removal of paint or to sand gel coat prior to the application of antifouling paint.
• After sanding remove sanding residue by wiping with a cloth that has been dampened with the proper solvent.
• Masking Tape– When it is necessary to mask off areas use a high quality clean edge masking tape, especially when the masking tape will be left on the surface for a long time.
• Brushes – For antifouling paints use a natural bristle brush but not necessarily one of as good quality as you would use to apply topside finishes.
• Rollers – Most solvent resistant rollers will have a phenolic core and will say that they are for use with oil based paints or epoxies. For antifouling paint and epoxy primers, use a 3/8”-1/2” nap roller.
Typically when people discuss bottom paint on a boat they are referring to Antifouling paint. Bottom paint prevents growth of organisms that attach to the hull and can affect a vessels speed, performance, and durability when boat is kept in the water for extended periods of time. If you don’t have that problem, you may not need bottom paint. Antifouling bottom paint typically has a flat, dull finish that is used below the waterline.
If you don’t have a growth problem or would like a nice shine to your boat’s bottom look to our other items like gelcoator a topside paint for moderate water exposure or an aluminum paint with no antifouling agents. Gelcoat adheres to most gelcoats or fiberglass/resins, see how to apply gelcoat. A boat bottom with antifouling will need to have it removed via sanding, sandblasting or bottom paint removerbefore a different type of paint will adhere.
There are generally two types of bottom paint both of which have several variations that create a multitude of products in the market place. The two different types or categories of bottom paint include hard bottom paintand ablative bottom paint.
Hard bottom paint is bottom paint that is a hard modified epoxy. After you apply hard bottom paint it is very durable and does not wear off.Hard bottompaints typically have a higher ratio of pesticides (usually copper) in them that are exposed in the outer surface of the bottom paint coating. As time goes by, the coating oxidizes and becomes less effective in combating marine growth. Hard bottom paint is generally used on boats when the boat sits for long periods of time without moving at all, or there is little movement of water (current/ tide) around the boat. You should not use a hard paint if you boat comes out of the water such as on a trailer or a lift. After 72 hours, the hard bottom paint will oxidize on the outer surface from the air and becomes ineffective. If you are trailering your boat, or keep it on a lift you should always use ablative bottom paint.
Ablative bottom paint, also known as self- polishing bottom paint, is softer and allows the coating to wear off at a controlled rate. Much like a bar of soap, once the boat moves in the water or there is a current and or tide, the outer layer slowly wears away. The wearing away of the self-polishing bottom paint allows for new, unoxidized paint to be exposed. Therefore, if you are trailering your boat, or it comes in and out of the water for any reason, the paint will oxidize within 72 hours. However, once placed back in service, that oxidized ablative paint wears away and exposes a new fresh outer coating with active protection. Ablative bottom paint is a newer technology then hard paint. It is the preferred bottom paint of most users since it typically lasts longer and continuously exposes a new active outer coating that protects against marine growth.
How long does bottom paint last on a boat?
In general, you should apply boat bottom paint once a year, however; some bottom paints can last for two years. If your boat is kept in the water or you use it regularly, you you have it checked annually to determine if it requires a new bottom paint coating.
The cost to paint the bottom of your boat depends on a number of factors including the size of your boat, the paint you choose and whether you use a primer or not. Other factors include whether you will paint your boat or hire someone to paint it. For example, Biocop TF by Sea Hawk, is a popular bottom paint and currently costs $275.77 a gallon and provides theoretical coverage of 315 square feet per gallon. If the bottom surface of your boat is 700 square feet you would theoretically need to purchase three gallons (Biocop is not offered in quarts) at a total cost of $827. 31 for the three gallons.
That may seem expensive for paint, however boat bottom paint uses antifouling properties in order to protect the boat’s bottom from organisms found in saltwater and other elements.
For information on calculating how much paint you need to paint your boat bottom you can refer to our Bottom Paint Calculator.
Apply Primer: Seal the surface with 2-3 coats of Tuff Stuff, or other high build epoxy primer. For Tuff Stuff, apply the ﬁrst coat of primer and allow the surface to dry to become tacky. Temperature and humidity affect the dry time, but you will know when to apply your next coat of primer once the paint ﬁlm becomes “tacky”. You should be able to ﬁrmly press your thumb into the paint ﬁlm and leave a thumbprint without any primer coming off the surface. You should use this method in between coats of primer and your ﬁrst coat of antifouling paint. When applying over multiple days, it is always best to go overnight between coats of primer instead going overnight between the ﬁnal coat of primer and the ﬁrst coat of bottom paint. Additional information can be found on the Tuff StuffTechnical Data Sheets.
Apply Bottom Paint: Apply minimum of two coats of Sea Hawk bottom paint. Allow 3 to 6 hours between coats and a minimum overnight dry. See the speciﬁc Technical Data Sheet for antifoulant being used. Some antifoulants may require more than 2 coats.
Sanding System** Better Paint Option
Sand and Clean: Sand to a uniformly frosty, dull looking surface with 80-100 grit (no ﬁner) sandpaper, remove any residue.
Apply Bottom Paint: Apply minimum of two coats ofbottom paint. Allow 3 to 6 hours between coats and a minimum overnight dry. See the speciﬁc Technical Data Sheet for antifoulant being used. Some antifoulants may require more than 2 coats.
Simple No Sand System ** Good Paint Option
Apply Primer: Apply one thin coating of 1266 Non-Sanding Primer. This coating is applied at a maximum of 1-2 mils WFT. Excessive buildup can cause a lack of adhesion. Minimum dry time is 20 minutes with a maximum of one hour.
Apply Antifoulant: Apply minimum of two coats ofSea Hawk antifouling paint. Apply ﬁrst coat of antifouling within 2 hours of applying primer. Apply 2nd coat of antifouling allowing 3 to 6 hours between coats and a minimum overnight dry.
Note: Do NOT use a copper based paint on metal running gear and parts. You should use a metal free bottom paint such as Sea Hawk Outdrive Paint, priming it withTuff Stuff first.
Preparation is key when painting on any surface. Applying bottom paint is not the cleanest of jobs, but it is really simple to do. Below you will find the exact steps to insure a good bottom paint job, whether you have a new boat, or a boat that has existing bottom paint on it.
Preparation for Bare Fiberglass When painting a bare fiberglass gel coat hull for the first time, it is extremely important that all contaminants such as grease, oil, wax, salt, or other foreign material are completed removed prior to sanding or application of a Sea Hawk System. Scrub the surface with a detergent soap and stiff bristle brush.
Clean your boat following options A or B
A. Clean and de-wax fiberglass hull withS-80 Wax N’ Grease Killer solvent based dewax. Saturate cheeseclothrag and wipe thoroughly to remove any cleaner and contaminants. Be sure to remove any residue before it dries and change rags frequently to insure contaminants are completely removed.
B. Apply S-90 De-Wax Etch & Cleaner with a maroon 3M Scotch-Brite® pad scrubbing thoroughly. Do not allow cleaner to dry on the surface and remove by flushing with water.Rinse entire surface with water and check for any beadingon the surface which will indicate that wax is still present. If necessary repeat step 2 again until the surface is contaminant-free. Choose your system below.
Apply Bottom Paint Apply a minimum of two coats of Sea Hawk bottom paint. Allow 3 to 6 hours between coats and a minimum overnight dry before launching. See the specific Technical Data Sheet for the bottom paint you are using. Some bottom paint may require more than 2 coats.
Tip: Epoxy systems on the bottom of bare fiberglass is the best way to protect your boat against blisters. It also provides added adhesion of the bottom paint to the hull.
Preparation Over Existing Bottom Paint
Clean the boat Clean the existing boat bottom paint with a pressure washing. If you have excess build up of growth, you can remove this by scraping and/or using muratic acid. Try to get all growth residue off the existing old bottom paint so that you have good adhesion of the new bottom paint.
Scuff Sand the surface
Scuff sand to a dull looking surface with 80-100 grit (no finer) sandpaper, then rinse with water and allow to dry. If your old bottom paint is really chalky, consider giving it a more agressive sanding to insure proper adhesion of the new bottom paint.
Apply Bottom Paint Apply minimum of two coats of Sea Hawk bottom paint. Allow 3 to 6 hours between coats and a minimum overnight dry before launching. See the specific Technical Data Sheet for bottom paint being used. Some bottom paint may require more than 2 coats.