How to Repair or Replace Your Boat's Rub Rail

Walk the boat and look at the rail and the joint behind it. Push on the rail: movement or a "crunch" means loose or failed fasteners. Look inside for water stains, rust trails or wet spots under the gunwale, and check your bilge after rain. Decide if this is an insert job or a full rail, and photograph everything.

Remove the end caps (usually a screw or two at each end). Start at one end and pull the old insert out of the channel. Clean the channel with a soft brush and soapy water and let it dry. Check the rail screws you can now see; snug any loose ones, and replace rusted ones one at a time with a dab of sealant.

Find the center of the new insert by folding it in half, and start at the bow. Warm a short section with a heat gun or by leaving the coil in the sun or warm water until it's flexible. Seat one leg in the channel, then press or tap the other in with a dead-blow mallet, working a few inches at a time down each side. Don't stretch the insert hard as you go: stretched vinyl shrinks back later and leaves gaps at the ends. Trim, secure the ends as your rail maker describes (often a screw through the end of the insert to stop shrinkage), and refit the caps.

Remove the end caps and insert. Then remove the screws or drill out the rivets, working one section at a time. On boats where the rail fasteners also clamp the hull to the deck, keep the rest of the rail in place until you're ready to reseal that section. Peel the rail off; use a plastic scraper to free it from old sealant without gouging the gelcoat.

Scrape away old sealant from the joint and the hull side. Clean with the solvent your new sealant maker recommends. Now look closely at the seam: gaps, cracked filler, loose screws in the joint itself, wet or soft spots. If the deck and hull separate when you press, or you see daylight or a big gap, stop and get a pro to look at the joint before you cover it up.

Fill old screw holes with epoxy filler or thickened epoxy so they don't leak or weaken the new screws' grip. Let it cure as the product says. Mark where the old holes were on masking tape above the rail line, so you don't drill into a filled hole that sits right where a new screw wants to go.

While the rail is off, reseal any open or cracked section of the joint with a marine sealant suited to the job, pressing it fully into the gap. BoatUS (Don Casey) notes that very high-strength polyurethane adhesives such as 5200 are close to permanent and make future removal hard; many owners prefer a medium-strength sealant here so the rail can come off again. Check your boat builder's recommendation if you can get it. Keep sealant out of screw holes you plan to reuse, and let it set as the label says before covering it.

Unroll the rail on grass or a smooth floor, not gravel or asphalt, which scratches the vinyl. Many vinyl kits start at the center of the bow (find the center by folding the rail), with the lip or flange on the side the maker shows. Check that the new rail fully covers the joint and the old holes. Have your helper hold it in place.

Drill pilot holes through the rail's holes (or mark and drill at even spacing if your rail isn't pre-drilled; the semi-rigid install Boating Magazine shows uses screws about every six inches). Dab sealant on each screw and on the back of the rail as the maker recommends, then drive the screw. Set your drill clutch low so screws stop flush; overdriving puckers vinyl and can crack the gelcoat around the hole.

Work aft from the bow, keeping the rail snug and straight with a slight stretch so it doesn't wave between screws. At the bow and the transom corners, warm the rail with a heat gun kept moving until it bends without kinking, then fasten it. Add an extra screw at tight curves and at the ends if needed.

If you need a second coil, butt the ends tightly as your kit describes and put a screw close to each side of the joint. At the transom, trim the rail and insert neatly (a hacksaw, knife or pruning shears) and fit end caps, or a splice cap where the two ends meet across the transom on inboards, sterndrives and bracket-mount boats.

Install the insert as in step 3. Tool squeezed-out sealant with a gloved finger, then pull the masking tape away from the rail before the sealant skins. Florida Sportfishing also suggests a thin bead of UV-resistant marine sealant along the top and bottom edges where the rail meets the hull, so dirt and salt water don't work in behind it; check that your rail maker allows this. After the cure time, hose the joint down hard (or wait for rain) and check inside for drips. Log the job and the sealant you used in BoatMend.