Here are the steps I use when drilling holes in fiberglass:
1. Use masking tape to cover the entire area you plan to mount your rod holder, depth finder or other accessory.
2. Hold the mounting base in the position you want it mounted.
3. Using a felt tip pen, mark the location of the screw holes on the masking tape. Take your time here!
4. Find the proper size drill bit for the hole size you intend to drill. Tip – Drill a test hole in a piece of scrap wood and set the screw there. The screw should fit snug, not real tight.
5. Now, find another drill bit about half the size of the one that will make the final hole. Using the reverse gear on your drill, start a pilot hole in each of the marked location. (Drilling in reverse right through the masking tape and slightly into the gel coat.)
6. Repeat the reverse drilling process with the drill bit that will make the final hole.
7. Switch the drill into forward and finish each hole. Carefully drill out each hole with the drill at full speed applying very slight pressure.
8. Remove the masking tape. The holes should have a “Clean” appearance. No cracking or spider webbing.
9. Apply a small amount of silicone glue to each hole (I use a product called “Marine Goop”. You only need a very small amount.
10. Mount the rod holder base (or accessory) with the proper screws. They should be stainless steel and are usually provided with the rod holder when purchased new.
Good Luck,
Jon J.