Fiberglass is one of the most durable materials used in boat construction but is not indestructible. Over time, stress, impact, UV exposure, and water damage can cause fiberglass to weaken, crack, or deteriorate. If left unaddressed, minor issues can escalate into structural damage, water intrusion, and expensive fiberglass repair.
Many boat owners overlook small signs of fiberglass damage, assuming they’re cosmetic. However, what starts as a small crack or blister can compromise your boat’s strength, performance, and resale value. Fiberglass damage doesn’t just affect the appearance of your boat. It can also impact its safety, efficiency, and longevity. Investing in timely fiberglass repair can prevent small issues from turning into major structural problems, saving you time and money in the long run.
In this guide, we’ll review nine warning signs that your boat’s fiberglass needs repair before it becomes a costly problem.
9 Ways To Know Your Boat Needs Fiberglass Repair
- Visible Cracks or Spiderwebbing
- Soft or Spongy Deck Areas
- Bubbling or Blisters on the Hull
- Water Leaks or Moisture Intrusion
- Fading, Chalking, or Peeling Gelcoat
- Unusual Vibrations While Boating
- Exposed Fiberglass Strands or Rough Patches
- Weakened or Loose Hardware Attachments
- Strange Noises or Creaking Sounds
1. Visible Cracks or Spiderwebbing
One of the most obvious signs of fiberglass damage is cracks or spiderwebbing on the gelcoat or hull. These small fractures often appear from impacts, stress, or repeated flexing of the fiberglass. While surface cracks may seem minor, they can allow moisture to seep in, weakening the structure over time.
Ignoring these cracks can lead to delamination or structural failure if water gets between the fiberglass layers. If you notice spiderwebbing around high-stress areas like the transom or near cleats, it’s time for a closer inspection.
When to Take Action:
- If the cracks spread or deepen over time.
- If water appears to be seeping from the cracks.
- If the cracks are near load-bearing areas of the boat.
2. Soft or Spongy Deck Areas
A solid fiberglass deck should feel firm and sturdy underfoot. If you notice soft, spongy, or flexing areas, it’s a sign that the core material beneath the fiberglass has rotted or delaminated. This is often caused by water intrusion through cracks, unsealed hardware, or failing caulking.
A soft deck can become a serious safety issue, as weakened fiberglass won’t provide the support needed under heavy foot traffic. If left untreated, these areas can collapse, requiring major repairs or even complete deck replacement.
When to Take Action:
- If the deck feels different in certain areas compared to the rest of the boat.
- If water is pooling in the soft spots.
- If you hear a hollow sound when tapping on the fiberglass.
3. Bubbling or Blisters on the Hull
Blisters form when water gets trapped between the fiberglass layers and the gel coat, creating small raised bubbles on the hull. These may initially seem like a cosmetic issue, but they indicate a serious problem—osmosis.
Over time, the trapped moisture breaks down the resin, weakening the fiberglass structure. If the blisters pop or crack, they can allow even more water to seep in, leading to expensive fiberglass delamination repairs.
When to Take Action:
- If blisters appear in clusters or keep recurring.
- If popping a blister releases a foul-smelling liquid (a sign of severe water damage).
- If blisters spread over large areas of the hull.
4. Water Leaks or Moisture Intrusion
Fiberglass is designed to be watertight, so if you notice water leaking into compartments, hatches, or bilges, it’s often due to fiberglass damage, cracks, or weak seals. If left unchecked, water intrusion can lead to mold, mildew, rot, and even electrical failures. The longer water sits inside the fiberglass layers, the weaker your boat’s structural integrity becomes.
When to Take Action:
- If you notice unexplained moisture buildup inside your boat.
- If water is seeping through deck fittings, windows, or seams.
- If you smell musty or moldy odors, this indicates trapped moisture.
5. Fading, Chalking, or Peeling Gelcoat
The gel coat is the protective outer layer of fiberglass, shielding it from UV rays, salt, and environmental wear. Over time, exposure to the elements can cause the gel coat to fade, chalk, or even peel away. A weakened gel coat makes your boat vulnerable to cracks, water intrusion, and further fiberglass damage. If your boat’s finish is no longer smooth or glossy, it may need professional refinishing or fiberglass repairs.
When to Take Action:
- If your boat’s finish feels rough, dull, or powdery.
- If you notice gelcoat peeling, flaking, or deep discoloration.
- If your hull absorbs water instead of repelling it.
6. Unusual Vibrations While Boating
Fiberglass damage can destroy your boat’s balance and stability, leading to increased vibrations or rough handling. Cracks, weak spots, or hull damage can affect how water flows against the boat, making the ride feel less smooth. In some cases, damaged stringers or bulkheads inside the fiberglass structure can cause the boat to flex more than normal, leading to vibrations at higher speeds.
When to Take Action:
- If your boat feels different while riding, especially in calm waters.
- If you hear rattling, creaking, or unusual noises while underway.
- If your boat is losing speed or struggling to get on plane.
7. Exposed Fiberglass Strands or Rough Patches
If you see fiberglass strands poking through the gelcoat or notice rough, frayed patches on your boat’s surface, your fiberglass is deteriorating. This often happens from years of wear, impact damage, or neglected maintenance. Exposed fiberglass can lead to delamination, water absorption, and structural weakness. Even minor abrasions can worsen over time, so repairs should be made as soon as possible.
When to Take Action:
- If you feel rough splintering areas on the hull or deck.
- If fiberglass fibers are sticking out from cracked or chipped areas.
- If a previously repaired section is showing signs of wear again.
8. Weakened or Loose Hardware Attachments
If screws, bolts, or cleats feel loose, it may be because the fiberglass underneath has weakened or cracked. Over time, constant stress and exposure to the elements can cause mounting points to deteriorate, making them less secure. This can be especially dangerous for cleats, railings, and ladders, as loose hardware can fail when you need it most.
For example, if your cleats or grab handles pull loose while docking, it could result in costly damage to your boat or another vessel. Weak hardware can also allow water to seep into the fiberglass, leading to further internal damage, rot, or delamination.
When to Take Action:
- If the hardware wobbles or shifts when force is applied.
- If water is seeping through screw holes or mounting points.
- If the fittings won’t stay tightened despite adjustments.
9. Strange Noises or Creaking Sounds
Your boat should feel solid and stable on the water. If you start hearing creaking, cracking, or popping sounds, it could mean that the fiberglass is flexing too much or developing stress fractures. These sounds often indicate that internal fiberglass layers are separating, weakening the overall structure.
Left untreated, it can lead to major hull failure or unsafe boating conditions. Boats that have been heavily used, stored improperly, or subjected to frequent impacts are especially prone to structural weakening, which can be costly to repair if not caught early.
When to Take Action:
- If your boat makes unusual noises when under stress or while moving.
- If you hear loud cracking sounds when hitting waves.
- If certain areas of the boat feel weaker than before.
