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How to Replace Worn Trailer Bunks or Rollers

My trailer bunks are rotting and scratching the hull — how do I replace bunks (or switch to rollers)?

Rotting bunks usually mean the wood failed years before the carpet did, and once the carpet wears through, exposed staples and bare board are what gouge your hull. The fix is straightforward DIY: replace the bunk boards with pressure-treated or composite lumber and marine-grade bunk carpet (or slick bunk slides), and stop reusing old staples. One thing the old how-tos miss: modern pressure-treated lumber is copper-treated and corrodes aluminum and plain steel, so on an aluminum or galvanized trailer use stainless/hot-dip hardware and keep the wet treated wood from sitting directly against the frame (or just use composite). Switching to rollers is a bigger job that changes how the boat loads — worth it for steep or shallow ramps, but for most ramps fresh bunks are the cheaper, more hull-friendly answer. Whatever you pick, get the boat off the trailer safely first; do not work under a hull held up only by a winch or jack.

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.

💵 $60-$180 DIY for two pressure-treated boards, marine bunk carpet, Monel/stainless staples, and stainless hardware; $150-$300 for composite bunk boards or a bunk-glide kit. Roller conversion kits run $150-$500+ in parts. A trailer shop typically charges $250-$600 for bunk replacement and $500-$1,200+ for a roller conversion depending on trailer size. ⏱ 2-4 hours for a bunk replacement and recarpet once the boat is off the trailer; a half to full day for a roller conversion or if hardware is badly corroded. ● Use caution
Safety: The real hazard here is crushing — a loaded boat trailer holds thousands of pounds, and a hull dropping off a winch, jack, or failed bunk can kill. Never put any part of your body under a hull supported only by the winch strap, the tongue jack, or a single jack; use rated jack stands or cribbing, keep the trailer on its chocked wheels, and work on level ground. If you do this near the water at a ramp, mind slip-and-fall and drowning risk on wet, algae-covered surfaces, and don't block a launch lane.

Common causes

How to fix it

  1. Get the boat off the trailer first if you can. The safest job is done with the boat in the water or blocked on stands. If the trailer must stay loaded, support the hull on jack stands or cribbing rated for the weight, keep it on its own wheels with the wheels chocked, and work on level ground — never trust the winch strap, the coupler/tongue jack, or a single bottle jack as your only support while any part of your body is under the hull.
  2. Measure and photograph everything before you remove a thing: bunk length, width, board thickness (usually 2x4 or 2x6 nominal), spacing from centerline, fore/aft position, and bracket angle. Note where the hull strakes and the keel land so the new bunks support structure, not just flat panel.
  3. Remove the old bunks by backing out the carriage bolts or lag screws from the brackets. Penetrating oil and a breaker bar help with corroded hardware; replace any fastener that is rusted, bent, or spins, and inspect the brackets themselves — copper-treated wood sitting wet against an aluminum or galvanized bracket often corrodes it from the inside out.
  4. Cut new boards from pressure-treated SYP lumber (specify KDAT — kiln-dried after treatment — so it isn't soaking wet and warping) or use composite/HDPE bunk board for a no-rot option. Note that today's PT lumber is treated with copper (ACQ/MCA) and is corrosive to aluminum and plain steel, so on an aluminum or galvanized trailer either isolate the wood from the frame (a strip of HDPE/plastic shim or barrier tape between board and bracket) or go composite/HDPE and skip the issue. Match the original dimensions and round or chamfer the ends so the hull slides on without catching.
  5. Cover the boards with marine-grade outdoor bunk carpet (or fit slick polymer bunk-glide caps). Wrap the carpet over the top and down both sides, pull it tight, and fasten ONLY on the underside or vertical faces with Monel or stainless steel staples plus a few stainless screws — never put a staple or screw on the top surface where the hull rides. Use stainless or Monel here, not plain steel: copper-treated wood plus constant freshwater/saltwater wetting rusts ordinary fasteners fast and electroplated 'galvanized' staples don't last.
  6. Re-mount the bunks to the brackets with new carriage bolts, nylon-insert lock nuts, and washers. Stainless or hot-dip galvanized are the right choices; avoid electroplated/zinc hardware in copper-treated wood. Set them to your measured positions so the hull lands evenly on both bunks and the keel rollers/keel support carry the keel.
  7. Load the boat and check the fit on a level surface: hull should sit centered, weight shared across the full bunk length, no rocking, and the transom/keel supported. Re-tighten hardware after the first launch, then recheck after a few trips as the carpet beds in.
  8. If switching to rollers instead: this changes load distribution from continuous (bunks) to point-loads (rollers), so the roller layout must match the hull and put rollers under solid structure, not thin unsupported panel. Use a roller conversion kit matched to your trailer frame and boat weight, keep keel rollers aligned dead on centerline, and confirm the hull is fully supported at rest. Fiberglass hulls generally do better on bunks; rollers shine on shallow or steep ramps where you launch and retrieve with the trailer barely wet. If unsure, keep bunks — a misconfigured roller setup can dent or stress-crack a hull.

DIY or call a pro?

Replacing bunks and recarpeting is a solid weekend DIY job for a competent owner with basic tools. Switching to rollers, or any trailer that needs frame welding, axle/spring work, or a boat you can't safely get off the trailer, is worth handing to a trailer shop. If you've never blocked a hull, have the marina launch the boat or lift it first so you're not working under a loaded trailer.

Tools & parts

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Based on: BoatUS / BoatUS Foundation (trailering and trailer maintenance guidance); BoatUS Trailering resources; NMMA (National Marine Manufacturers Association); Boat and trailer manufacturer owner's manuals (bunk/roller setup and load support); American Wood Protection Association / treated-lumber fastener-compatibility guidance (copper-treated wood corrosion)

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.