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How to Repair Keel and Skeg Damage After a Grounding

I ran aground and chewed up the bottom of my keel — how do I fair and seal the damage?

Cosmetic gouges in a keel are a weekend fairing job, but the real risk after a grounding is hidden structural damage you cannot see from the chips. The keel-to-hull joint takes a huge shock load when you stop hard, so before you grind and fair, inspect for cracks at the hull/keel seam ("keel smile"), loose keel bolts, water weeping from the laminate, and on a fin keel any sign the keel shifted. If it's a lead/iron fin keel or there's any seam cracking, get a surveyor or yard to assess the joint and bolts before you touch the fairing — sealing over a compromised joint hides a sinking or rig-loss hazard. Note up front: grinding a lead or iron keel makes toxic metal dust, so eye/lung protection and dust control are not optional.

ℹ️ Reference only: For general reference only. This guide does not guarantee any result — every home is different. Verify against your local building codes and a licensed professional before acting, especially for electrical, gas, plumbing, structural, or roof work.

💵 $100-$400 DIY for a cosmetic fair-and-seal (epoxy, glass, fairing filler, barrier coat, antifoul), excluding haul-out. $500-$2,000 at a yard for cosmetic-plus-fairing with haul-out. $3,000-$15,000+ if the keel must be dropped, re-bedded, and bolts replaced, plus survey fees. ⏱ A cosmetic DIY repair is 1-2 weekends plus epoxy/barrier-coat cure time (drying the laminate can add days to weeks). Structural joint or keel-bolt work is typically 1-3 weeks at a yard. ● Use caution
Safety: Three real hazards. First, mechanical: never work under a keel supported only by jack stands — the hull weight must sit on keel blocks or a cradle, or the boat can shift and crush you. Second, the failure-mode hazard: sealing over a damaged keel joint or loose keel bolts can let the joint open at sea, which can sink the boat or, on a fin keel, contribute to rig/keel loss. Treat any 'keel smile,' loose bolt, or sump crack as structural until a surveyor says otherwise. Third, toxic dust: grinding or sanding a lead or iron keel releases lead/metal dust that is harmful to inhale or ingest — wear a P100 respirator, contain the dust on a tarp, clean up and dispose of grindings properly, and keep food and drink away. Also wear a respirator, gloves, and eye protection for grinding fiberglass and mixing epoxy — the dust and uncured resin are sensitizers — and grind in a ventilated space.

Common causes

How to fix it

  1. Get the boat hauled and blocked safely before doing anything. Never work under a keel that is only on jack stands without the hull weight carried on a proper keel block or cradle — a shifting boat is a crush hazard. Jack stands are for stability, not for carrying the load. Let the keel dry; lead and iron hold water in cracks for days.
  2. Inspect for structural damage first, not cosmetics. Look for cracking or gaps along the hull-to-keel joint (the 'keel smile'), rust weeping (iron keel), water seeping from the laminate, movement of the keel when nudged, and on internal inspection any cracking in the keel sump or stress cracks around keel bolts/floors. Check keel-bolt condition. If you see joint separation, loose/corroded bolts, or sump cracks, STOP and bring in a surveyor or yard before sealing anything.
  3. Tap-test and probe the damaged area. A sharp screwdriver or a phenolic hammer reveals delamination (dull thud) and how deep the gouging goes. Grind out all loose, cracked, or water-saturated material back to sound, dry laminate or solid metal — a clean repair needs a clean substrate.
  4. Let any wet laminate fully dry. Moisture-meter it or give it days to weeks in warm dry air. Trapped water under a new barrier coat will blister and the repair will fail.
  5. Rebuild structure with the right materials for the substrate. On GRP/encapsulated keels, rebuild with marine epoxy (e.g., West System or equivalent) and biaxial glass cloth, wetting out each layer and overlapping onto sound laminate. On lead/iron fin keels, clean to bright metal, prime per the system (iron needs an epoxy metal primer to stop rust; lead needs abrasion/etch and an epoxy primer for adhesion), then build up with epoxy thickened with high-density filler. Use marine-grade epoxy, not polyester filler or hardware-store body filler, below the waterline. WARNING: grinding/sanding lead or iron produces toxic metal dust — wear a P100 respirator, catch the dust on a tarp, and dispose of it properly; do not let lead grindings wash into the ground or water.
  6. Fair the rebuilt area. Trowel on epoxy fairing compound (epoxy + low-density fairing filler, e.g., West 407/410), shape with long boards, and sand fair to the original keel profile. Fairing fillers are for shape only — never use lightweight fairing compound as the structural fill.
  7. Re-establish the moisture barrier. Apply the appropriate number of epoxy barrier-coat coats (e.g., a barrier system like Interlux InterProtect) over the whole repair and surrounding area, following the maker's wet-on-wet recoat windows. This is what actually 'seals' the keel against water intrusion.
  8. Re-bed the keel joint only if it was disturbed. If the joint opened, that is a yard/surveyor job: the keel must be dropped or the joint reefed out, keel bolts inspected/replaced, and the joint re-bedded with the yard-specified compound and bolts torqued to the builder's spec. Note that 3M 5200 is a permanent adhesive — it bonds the keel on and makes a future keel drop very hard, so many yards prefer a flexible polyurethane/polysulfide bedding; follow the boatbuilder's spec. Do not just smear filler over a smile.
  9. Antifoul to finish. Once the barrier coat is cured, apply bottom paint compatible with your existing system over the repair to match the rest of the hull.
  10. On the water afterward, watch the bilge for new water intrusion the first few sails and have the keel-bolt condition re-checked after a season.

DIY or call a pro?

Cosmetic gouges, abrasion, and barrier/antifoul repair on a sound keel are well within a competent owner's skills once hauled. Anything involving the keel-to-hull joint, keel bolts, a cracked sump, a shifted keel, encapsulated-ballast cracks, or skeg/rudder structure is yard-and-surveyor territory — those carry sinking and rig-loss risk and often need the keel dropped. When in doubt about whether damage is structural, pay for the survey; it's cheap insurance.

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Based on: BoatUS / BoatUS Foundation; ABYC (American Boat & Yacht Council); US Coast Guard / USCG Auxiliary; NMMA (National Marine Manufacturers Association); Epoxy/coatings manufacturer guidance (West System, Interlux/Interprotect); SAMS / NAMS marine surveyor associations

General marine-maintenance guidance, not a substitute for a qualified marine technician or surveyor. Boats and conditions vary; for fuel, electrical, fire, or structural issues — or anything safety-critical — consult a professional. Always follow your engine and equipment manuals.