For boat owners and marine pros, choosing the right fiberglass putty is key to durable repairs. This guide highlights five top options that are widely used for bonding, filling, and fairing on boats. Each product is suited to different materials and repair scenarios, from hull-to-deck bonding to filling holes and chips. Best for structural repairs, easier application, or extended working time, these picks cover common needs on fiberglass, wood, and metal surfaces. Below is a quick comparison to help you decide which filler fits your project.
| Product | Best For | Format | Key Benefit |
|---|---|---|---|
| TotalBoat Polyester Structural Repair Putty (Quart) | Structural bonding and filleting | Quart | Long strand fiberglass reinforcement |
| Fiberglass Warehouse Structural Polyester Putty (Quart) | Bonding dissimilar surfaces | Quart | Orthophthalic polyester with fiberglass reinforcement |
| Globalcom Fiberglass Boat Repair Kit | General repair kit for chips, cracks, holes | Kit | Durable, UV resistant, easy-to-use |
| TotalBoat Polyester Structural Repair Putty (Gallon) | Large-area fills and decks | Gallon | Same resin family as quart, higher quantity |
| TRUE COMPOSITES Structural Polyester Bonding Putty | Versatile marine bonding | Quart | Fiber-reinforced, sag-resistant |
TotalBoat Polyester Structural Repair Putty – Quart Kit
TotalBoat’s marine-grade filler uses pre-thickened, long-strand fiberglass-reinforced polyester for strength and elasticity. It is designed for bonding decks, stringers, liners to hulls, and filling screw or bolt holes. Works above or below the waterline, with a 15–20 minute working time at 70°F when catalyzed with MEKP. This option is best for structural filling and filleting where rigidity and impact resistance matter. Limitations include careful catalyst control to avoid running or sag on vertical surfaces.
Who this is best for
Boat builders and repair techs needing a high-strength filler for structural joints and bulkhead bonding.
Notes
Follow the recommended catalyst amount to control working time. Paste-like consistency helps prevent sag, but larger jobs may require multiple applications or longer cure times.
Fiberglass Warehouse Structural Polyester Putty (Quart)
This Advanced Ortho Structural Putty uses orthophthalic polyester resin blended with glass fibers to create a strong bond for bonding hulls, decks, and bulkheads. It’s easy to mix and apply with a putty knife, offering a long working time and sandability after curing. It suits boat-building tasks as well as repairs that require adhesion to dissimilar substrates like fiberglass, aluminum, wood, and composites. A caution is that overall cure times can vary with temperature and catalyst levels.
Who this is best for
Owners and professionals focusing on bonding dissimilar surfaces or performing large-area structural repairs.
Notes
Ensure the repair area is clean and dry for best adhesion. Sanding after cure will yield a smoother finish for final coatings.
Globalcom Fiberglass Boat Repair Kit
The Globalcom kit provides a multifunctional marine fiberglass repair solution suitable for chips, cracks, pits, gouges, scratches, and holes across watercraft types. It promises strong adhesion after curing, UV resistance, and water resistance to endure harsh marine conditions. It’s easy to use: clean, mix in a 1:1 ratio, apply, cure for 24 hours, and sand to smooth. Best for quick, all-around repairs and for owners seeking a ready-to-go kit rather than individual components.
Who this is best for
Casual repair projects or maintenance crews needing a complete kit for common fiberglass issues.
Notes
Surface preparation and proper ventilation are important during mixing and curing. Sanding after curing helps achieve a feathered edge for painting or coating.
TotalBoat Polyester Structural Repair Putty – Gallon Kit
This gallon version mirrors the quart’s formula with pre-thickened polyester resin and long-strand glass fibers for enhanced strength and elasticity. It’s ideal for larger repairs, bulkhead bonding, and deck-to-hull connections. Working time remains 15–20 minutes with MEKP at 70°F, enabling extended fairing and shaping for bigger jobs. A potential drawback is the larger volume requiring careful storage and usage planning to avoid waste over time.
Who this is best for
Professional shops or serious DIYers tackling large-scale structural repairs and deck or hull bonding projects.
Notes
Plan a spread-and-sand workflow to minimize sag and ensure a smooth finish; temperate environments help maximize working time and cure quality.
TotalBoat TotalFair Marine Epoxy Fairing Compound (2 Pint Kit)
TotalFair is a high-strength, lightweight two-part epoxy filler designed for fairing and filling dents, holes, and gouges on boats and other surfaces. It forms a waterproof bond and cures to a smooth finish suitable for final coatings. The 1:1 mix ratio makes it straightforward to use. This product is best for clean fairing work and for projects where a durable epoxy finish is preferred over solvent-based fillers.
Who this is best for
Owners seeking an epoxy-based filler for waterproof repairs and precise fairing on fiberglass, wood, aluminum, or steel.
Notes
Follow the recommended mixing ratio and allow complete curing before sanding and painting for best results.
TRUE COMPOSITES Structural Polyester Bonding Putty
TRUE COMPOSITES offers a marine-grade, fiber-reinforced polyester bonding putty designed for boat and automotive repairs. It spreads smoothly with a sag-resistant formula and provides strong bonding to fiberglass, wood, metal, and ceramics. Working time is adequate for feathering and shaping, with a focus on durable, long-lasting repairs in marine environments.
Who this is best for
Users needing a versatile, sag-resistant putty for bonding multiple substrates in a marine setting.
Notes
Best results come from clean, dry surfaces and gradual, feathered applications to avoid dips or edges that require additional smoothing.
Buying Guide: Key Considerations For Choosing Fiberglass Putty
What surface are you repairing? Choose a filler compatible with fiberglass, wood, metal, or composites to ensure strong adhesion. For hull-to-deck or deck-to-hull work, prioritize high-strength, fiber-reinforced formulations.
Do you need quick or long working time? If you’re a DIYer or working in tight spaces, a 15–20 minute window at 70°F can help control sag and achieve a smooth finish. For larger projects, a gallon-size filler can be more economical.
Are you aiming for a waterproof finish? Epoxy-based fillers offer excellent moisture resistance, while polyester fillers provide fast cure and easy sanding. Consider the final coating and exposure to water when choosing.
What level of sandability and finishing is required? Some putties cure hard and are easy to sand; others offer smoother feathering for painting. Test a small area to confirm finish quality before full application.
Storage, shelf life, and catalyst handling matter. Pre-thickened, fiber-reinforced products can be ready-to-use but require temperature-controlled storage. Always follow resin and MEKP catalyst safety guidelines.
FAQ
- What is the best putty for boat hull repairs? — Fiber-reinforced polyester putties with long-strand glass fibers offer high strength and elasticity, suited for hull repairs and bonding.
- Can these putties be used above and below waterline? — Yes, many marine-grade fillers are designed for use above or below water, but always check product specifics and cure conditions.
- What working time should I expect? — Most options provide 15–20 minutes at 70°F with catalyst; adjust for temperature and project size.
- Do I need to sand after curing? — Yes, sanding helps achieve a smooth edge before final coating or paint.
- Are epoxy fillers better than polyester for marine use? — Epoxy fillers tend to be more waterproof and bond to a wider range of substrates; polyester fillers cure faster and are easier to sand.
- Is a repair kit sufficient for large projects? — For large areas, consider gallon-size fillers or multiple applications to ensure structural integrity and even curing.