Basic Boat Repair

Locating a Leak

It is not uncommon or unusual to discover water in your hull on occasion. Most often, water gets in the hull from either a missing stern plug or a port lid that has not been screwed down properly. Another source can be old or missing silicone around the screws. However, on occasion you may find water inside the boat that cannot be explained for these reasons. The first step you need to take is to try to determine the source of the leak. With this information, we can tell you what steps you can take to remedy the problem.

The way we do it here at the shop is to make sure that the port cover is in tightly, then blow several large breaths of air into the drain hole (gently, do not over-pressurize!), and then quickly plug it with a stopper. Next go around the boat with a squirt bottle full of soapy water and spray at any and all suspect area’s as well as vulnerable spots, such as around any screw or bolt, the port ring, fin slot and deck edge. If you see areas where it’s blowing bubbles, that will be the source of your leak.

Repairing Scratches, Dings, Air Bubbles

For areas that are smaller than a dime and not deep enough to require a carbon/glass repair. If you get something slightly larger, but still not deep enough to warrant the larger repair, then you can fill the beveled area with auto body filler, then spray with gelcoat, sand and polish (see steps #6 – 9 of “Repairing small cracks and holes” below).

Using a new sharp razor blade or utility knife blade as a scraper, bevel the edge of the area you want to fill (all the way around)

Wipe area clean with acetone

Fill with catalyzed gelcoat – leave a little proud (overfilled) to allow for shrinkage

Allow to cure completely

Sand to smooth (1000) and polish

Repairing Small Cracks and Holes

These instructions are for damage that is large enough to cause a leak or to break through the fiberglass – for smaller repairs see ” Repairing deep scratches, dings and air bubbles” above.

Supplies you may need to do a repair:

Rubber gloves – for resin and gelcoat mixing and application

Respirator, or at minimum dust mask – for application of resin and gelcoat

Scotchbrite pad

Preval sprayer (available at hardware stores)

Wet/Dry sand paper, various grits

Epoxy Resin – we recommend West Systems (do not use “Marine tex “as it is not compatible with our materials)



Heat resistant plastic film such as Turkey oven roasting bags

Squeegee type tool (soft plastic w/straight edge on one side – (a Bondo spreader also works well)

Auto body putty (Bondo) and catalyst

Rubbing compound

Finishing polish (such as 3M Finesse II)

  1. Rough up gel coat with Scotchbrite pad around damaged area (to approximately 3 -4 times the size of the damage)
  2. Cut pieces of carbon or glass fiber cloth to shape. A typical repair will use 2-3 layers of carbon or 3 -4 layers of glass.
  3. Cut the first piece about 1” bigger than the damaged area and each successive piece about ½” larger (all the way around) than the first piece.
  4. Mix resin. Paint a coat of resin on damaged area. Apply cloth patches starting with the smallest piece, saturate each piece as it is applied. Don’t use too much resin. Don’t work in direct sunlight.
  5. Stretch and tape plastic film* firmly over repair. Use a squeegee or similar tool to push excess resin out from the patch (this will help to smooth and compact the patch). Clean this excess up with acetone quickly before it hardens. Apply masking tape to the remaining open edges of the film.
  6. When resin has hardened remove plastic and sand down high spots and edges, don’t remove too much material.
  7. Do final smoothing and faring with auto body putty. Sand to 220 grit sandpaper prior to painting.
  8. Paint with catalyzed gelcoat using a spray gun or Preval sprayer
  9. Wet sand to 1000 (start with 400 and work your way toward 1000 for finest finish).
  10. Buff with rubbing compound, then polish with finishing polish.

Repairing Split Deck Edge

Make sure the boat is very dry inside.

Tape off with masking tape around the area that you will be working in, to help keep the repair neat and confined.

Using some Popsicle sticks or a putty knife, pry open the area and sand with 80 grit sandpaper.

Mix a 2 part epoxy (use a high quality brand such as West Systems) with some “glass bubbles” or “micro balloons” to the consistency of pancake batter.

Use this mixture to fill the area that you have just sanded – use lots. Remove the Popsicle sticks or putty knife and tip the boat on its side so that the mixture will pool around the inside of the area and cure in that position.

Clamp shut by using masking tape pulled tight.

Resin and Gelcoat Mixing (not for spraying)

In a heat resistant container (i.e. paper coffee cup) mix about 1 Tablespoon gelcoat or resin with 2 – 4 drops catalyst.

Be sure to wear hand protection such as rubber gloves and eye protection.

For West Systems Epoxy, follow manufacturer’s instructions.

Spraying Gelcoat

Reduce w/acetone by 20 -30%

Catalyze @ 8-12cc per pound or 1 – 1 ½% with Quickset Super MEKP catalyst.

Spray 8-10- mils thick over repaired area. When set, spray PVA film over the gelcoat to promote curing. Wait 12 – 24 hours before sanding.