Follow Me on Pinterest Remodeling and Home Design

How to Touch Up Marine Gelcoat with Preval

Posted on Monday, November 19th, 2012 at 4:54 PM

The Condition of your Gelcoat Reflects the Value of Your Boat 

How to repair gelcoat with PrevalYachts, powerboats, jetskis and amphibious vehicles are coated with several layers of gelcoat, as  to protect the fiberglass hull from wear and damage. Gelcoat is a strong resin that adheres to the contours of your boat and flexes with the hull's contortions as it tackles the waves and weather.

If you get a lot of enjoyment out of your marine vehicle, the hull of is destined to suffer some wear. Regular docking, unforeseen events and heavy sunlight can take their toll, and even a few small blemishes can have a negative impact on the resale value of your nautical vessel. Professional hull scratch and gelcoat repairs can be expensive and inconvenient, so consider fixing it up yourself with a few simple tools and a Preval Sprayer or vFan Airbrush System.

Gelcoat is a polyester resin with many unique qualities, so the proper application of gelcoat is as much art as it is science. Regardless of your skill level with gelcoat application, the consistent spray pattern and portability of the Preval Sprayer make it an ideal tool for gelcoat boat repair touch ups.



Latex gloves
Eye protection

Wet/dry sanding blocks with grits #220, #320, #600 or #800

Clean rags or paper towels
Gelcoat and hardener – matched to the make and color of your boat
Preval Sprayer, or

vFan Airbrush System 

Auto-body filler, lacquer putty or acetate


  • Scraper, grinder or Dremel tool
  • Buffer
  • Polishing compound



  • This How-To is focused on gelcoat touch ups. For a complete refinish of your boat, industrial spray equipment will be required. 
  • Do not apply gelcoat if the temperature is below 65 or above 80 degrees Fahrenheit.
  • Use sanding blocks, not paper, for a more even finish. 
  • When filling corners and small chips, use acetate instead of bondo or lacquer filler.
  • Never spray gelcoat in direct sunlight during a hot day. The material will dry too quickly, resulting in cracks and/or a dull finish. 
  • Do not use wax-lined cups for mixing gelcoat, epoxy or resins, as these will leave small shavings in the mix and disrupt your Preval sprayer. 
  • Do not use any filler with fiberglass strands added.
  • Clean the Preval Sprayer by spraying through the unit with acetone, then save for later use.



  1. Put on respirator and eye protection to protect yourself from fiberglass dust and the gelcoat fumes.    
  2. Grind out loose fiberglass and gelcoat with a Dremel, drill or grinding tool.
  3. Wet sand on and around the scratch to eliminate all loose gelcoat.  
  4. Block sand the area and several inches surrounding it, starting with heavy grit to get chips and other loose materials, then moving to finer grits until the scratch and surrounding area is smoothed out.  
  5. Brush off the sanded surface, then clean it with acetone, using a one-direction wiping motion and paper towels or a clean rag to ensure the dust isn't smeared in.
  6. Fill the scratch with auto body filler, lacquer putty or fairing compound. Apply as much as needed, thinly and evenly. Wipe away the excess but leave enough to allow for sanding, then let dry.
  7. Sand the filling compound with #600 or #800 grit block then brush and wipe away all dust. Ensure the filler is even and smooth. If another coat of filler is needed, repeat Step 5.



  1. Put on latex gloves, respirator and eye protection.
  2. Mix gelcoat compound with hardener according to instructions, then pour the mixture into the Preval Sprayer or vFan Airbrush bottle. 
  3. Thin the gelcoat with a small amount of acetone to allow for an even spray.
  4. Keeping a consistent distance from the repair area with each pass, apply an even layer of gelcoat to the sanded area then allow to dry for 15-20 minutes.
  5. Repeat Step 8 until a minimum of five coats of gelcoat have been applied with the Preval Sprayer or vFan Airbrush.
  6. PLEASE NOTE: Some gelcoat brands recommend light sanding between layer applications. Please review the instructions carefully.
  7. After the final layer of gelcoat is dry, sand the area lightly and evenly with a #260-grit wet/dry block, then with a #320 and #600
  8. Finally, buff the area out with a clean buffer and polishing compound.