How to Replace Folding Boat Seat Hinges and Fix Back-to-Back Seats

Fold and unfold the seat several times and rock it in each position. Watch where the movement happens: the hinge pin itself (a worn or bent hinge), the screws (stripped holes or rotten wood), or the latch (out of adjustment or worn). A seat that won't stay up or down is often just a latch or a worn spring. A seat that sags or rocks is usually the hinge or the wood.

Photograph the hinge, latch, spacers and screw positions from a few angles before you touch anything. Then unscrew the seat or cushion from its hinge, or the hinge from the boat, whichever is easier. Put the screws in labeled bags. If screws are seized, soak them with penetrating oil and use a screwdriver bit that fits the head snugly so you don't strip it.

Look for rust streaks, a bent leaf, an oval or loose pin, and cracks around the screw holes. Brown staining on "stainless" hinges is common. BoatUS explains that even good stainless corrodes when it sits wet without oxygen, such as inside soggy wood. Pitting near the pin or cracks mean replace it. Light surface staining can be cleaned, but a hinge that wobbles on its pin won't get better.

Most seat bottoms and lids are plywood under the vinyl. Push an awl into the wood around each screw hole. Firm wood resists; soft, dark or crumbly wood is rotten, and new screws won't hold there. Press on the panel and see if it flexes. If the vinyl is stapled over the wood, pull back a corner to look at the edges, since water usually gets in at the edges and the screw holes first.

• Sound wood, stripped holes: fill and re-drill (step 6).
• Soft spots only around the screws: dig out the soft wood, let it dry and fill with thickened epoxy (step 6).
• The panel is rotten or delaminating: make a new base (step 7). Epoxyworks points out that once plywood has delaminated from moisture, the only real repair is new wood, and the same applies to a seat base.

Drill each damaged hole a bit oversize so you reach clean wood, let it dry, then fill it with thickened epoxy. After the epoxy cures, drill a new pilot hole through the plug. The screw now bites into solid epoxy instead of mushy wood, and the epoxy seals the end grain so water can't wick in again. Don't just jam a bigger screw into a rotten hole; it holds for a weekend.

Remove the vinyl and foam carefully: pull the staples instead of cutting the cover, so you can reuse it or use it as a pattern. Trace the old base onto new marine plywood (or a plastic or composite board), cut it out, and drill the same holes and drain holes. Seal plywood on every face and edge, including inside the holes, with epoxy or a good marine finish. Raw edges are where water gets in. Then put the foam and cover back on, or see the seat cushion guide if the foam is soaked.

Line the new hinge up with your photos and check that it folds the right way and the seat clears the boat, the console and any other cushions through its full swing. Mark and drill pilot holes. Use stainless screws or bolts sized to the hinge holes (don't mix steel or plated screws with a stainless hinge). Where the seat base allows it, through-bolt the hinge with washers and locking nuts rather than screws. BoatUS's backing plate article shows that a bolt with only a small washer has very little area to resist pulling through, so a large washer or a small plate under the nuts makes a big difference on a seat that people lean back on. Snug the fasteners evenly; don't crush the wood.

For a seat that's hinged to the floor, or a bench base screwed to the deck, treat every hole as a possible leak. BoatUS's seat-mounting advice is to fill old holes with epoxy and coat the threads of each new screw with a flexible marine sealant, because the pounding of a boat slowly crushes the wood fibers and opens a path for water. Through-bolt with a backing plate if you can reach underneath; see seat pedestal mounts and through-bolting accessories.

Fold the seat into each position and check it locks with a positive click and doesn't rattle. Most latches have slotted holes: loosen the screws, slide the latch or striker until it engages cleanly, then tighten. If a spring clip or detent is worn smooth, replace it. On back-to-back seats, check that each section rests on its stop or support leg, not on the hinge alone, when it's laid flat. A hinge that carries a person's weight with nothing under the seat will bend again.

Bench and locker lids with twist (cam) latches: if a hinged seat lid thumps and rattles in a chop, the latch is often loose rather than the hinge being worn. Mercury's quick tip: with the latch locked, tug the handle; more than about 1/8 inch of play means it needs adjusting. Open the lid, loosen the small set screw that holds the cam (the flat or Z-shaped hook under the rim) just enough to spin it, turn the cam two or three full turns clockwise, then snug the set screw and test. Full turns keep the cam and handle lined up when locked. If it becomes hard to twist, back the cam off a turn. A tight lid also keeps moisture out of the storage space under the seat.

Rinse salt and sand out of the hinge and latch with fresh water and let them dry. Apply a light lubricant that's safe for vinyl to the pin and moving parts, and wipe off the excess so it doesn't stain the cushions. Work the seat through its motion a few times.

Sit down hard, lean back, and push on the seat back and bolster from different directions. Fold and unfold it a dozen times. Recheck the screws after the first couple of trips, and log the job in BoatMend.