How to repair holes in fiberglass boat?

So, you did not see the stump hiding under the suface of the lake and now you have to patch a hole in your fiberglass boat? No worries. With a little patience, the right products and some elbow grease, you will be back in the water in no time.

If the damage to the hull is below the waterline or thought to be extensive, you must remove the boat from the water or run the risk of having your vessel sink. Affected areas above the waterline can be repaired with your boat still in the water.

Once your boat is in the proper area for inspection, what want to do is find out how severity of the damage. If the fiberglass damage is below the waterlineThe best way to do this is with the handle of a screwdriver. Use the handle to tap around the area to be repaired. Should you hear a solid thump, the damage is more than likely minimal; however, should tapping the damaged area give off a dull sound, the damage is probably more extensive. Once you know what you are facing, it's now time to get started.

For this repair, we will examine how to repair a small to moderate area of damage. The materials you will need are polyester resin and hardener, fiberglass matting, fiberglass cloth, expanding spray foam (for backing), acetone, paint roller and protective gear (eye protection, gloves, dust mask/respirator and coveralls or other protective clothing).

• The first step is to actually enlarge the hole. Using a disc sander or even a drill with disc attachment, grind off the rough edges of the hole until you get to a sturdier surface (making the hole about 3 inches wider). Sanding will remove loose material and any wax or gelcoat on the boat surface, making a stronger repair
•  Once the grinding is finished, use acetone to clean the area of repair (caution-acetone is highly flammable. Use in a well ventilated area and be certain to wear protection). Cleaning the area will allow the resin to stick better.
• Fill the hole with the expanding foam. Remember: It expands so don't fill too much. Once the foam has set, sand the foam even with the hull
• Mix the fiberglass resin and hardener by following manufacturer's directions and apply to area to be repaired
• Cut a piece of fiberglass matting slightly larger than hole and place into mixture painted over foam filler
• Cut several pieces of fiberglass cloth, one slightly larger than other (when stacked upon each other, you should notice only a slight raise in the surface). Brush the resin/hardener mixture onto the strips and starting with the shortest section, begin stacking on on top of the other until there is only a slight lump over the repair area.
• All repair to dry completely (approximately 6-8 hours) then sand smooth.
• Consult with your boat supply dealer for appropriate gel coat for your application

If you buy quality materials and exercise a little patience, you will be back on the water in no time with a sturdy, cost effective repair. Just watch out for the stumps.