Draining

• Before you repair the holes, you need to see if water has collected within the boat from the leak. If it has, you need to remove the water. You may be able to drill small holes into the hull, hang the boat where the water will drain and then repair the man-made holes like you will the other leaks. If this won't work, or if you don't want to add extra leaks to the boat, you need to remove the side entirely to drain out the water and then reattach it.
  
  

Filling Leaks

• You will be working with strong chemicals in most cases when filling in damaged areas, so protective goggles and gloves are a must. If you are dealing with cracks, it may help to first sand down the damaged area to the level of the surrounding fiberglass. Pinholes may not need this. Fill in the crack or hole with a resin-based putty using a putty knife. For pinholes, you can instead use a gelcoat, depending on whether you can get one close to the hull's original color. Apply enough gelcoat or putty so it rises above the level of the hull's surface; this ensures that the damage is completely sealed. Let the putty/gelcoat dry and set; this can take up to 24 hours.
  
  

Applying the Finish

• Sand down the filled-in area until it is level with the surface. If you only worked on the damaged areas, this is the only area where you need to apply the finish. Mix and apply an epoxy resin to the area; this resin can begin hardening immediately after mixture, so you need to work quickly. Lay a fiberglass patch on the epoxied surface. With this patch on top, you'll need to wait another 24 hours for the resin to set. Once it's dry, sand it down again if needed and apply a layer of gelcoat, making sure it covers a foot around the repaired area. If you had to remove the side of the boat to remove water, you'll likely need to apply more fiberglass to the entire side of the boat. Coat the entire surface in laminate resin and lay a whole fiberglass sheet to the coated area. You may need to repeat this up to two times. Once you have laid the last fiberglass sheet, apply one last coat of resin and wait for it to dry.