How to Fix Leaking Hatches and Portlights

Dry the inside completely. Have a helper below with a flashlight while you run a gentle hose stream around the hatch or port, starting low and working up: first the frame edge on the deck, then the gap between lid and frame, then the edge of the lens. Watch where the first drop appears and mark it.

On an opening hatch or port, close it on a sheet of paper at several points around the edge and latch it normally. If the paper slides out easily anywhere, the gasket is not being squeezed there. Note those spots.

Lay a straightedge along the sides of the lid and corner to corner. A bent lid, loose hinge pins or worn latches (dogs) can keep the gasket from closing evenly. Many hatches and opening ports have adjustable latches or hinge screws; check the maker's instructions before replacing parts.

Clean the gasket and the surface it seals against with mild soap and water; grit and dried salt can stop a good gasket from sealing. If the rubber is flattened, cracked, hard or shrunk so there are gaps at the corners, replace it with the gasket made for your model. Remove the old one, clean the channel, and fit the new one without stretching it. Where the ends meet, follow the kit instructions; a tight, clean joint matters.

Inspect the clear lens in good light:

• Cloudy but smooth: usually surface wear. SAIL suggests a plastic headlight polishing kit can bring back some clarity.
• Crazed: a web of fine cracks inside the plastic. Polishing will not remove it, and the lens has lost strength.
• Cracked through, discolored or brittle: replace the lens.

Clean lenses only with mild soap, water and a soft cloth. Avoid ammonia glass cleaners and solvents.

On many hatches the lens is bonded into the frame with sealant. A small leak at the edge is tempting to "touch up," but sealant does not stick to old sealant. The reliable fix is removing the lens, cleaning the frame to bare metal and resealing it, or fitting a factory lens kit. Some makers sell complete replacement lids, which is often easier than resealing an old one. Hatch rebuild shops also do this work.

This is where most DIY hatch jobs go wrong:

• Polysulfide (Life-Calk and similar) can attack plastic. BoatUS warns against it on polycarbonate (Lexan), and SAIL says never to use it for bedding plastic portlights.
• Polyurethane adhesive sealants (5200 type) are a poor match for plastic lenses as well, and rigid adhesives fail because acrylic grows and shrinks with temperature much more than fiberglass.
• Silicone is the usual choice for bedding plastic lenses into frames. For surface-mounted lenses, SAIL recommends a high-strength structural glazing silicone, and Practical Sailor has had good results with thick butyl hatch-mounting tape.

Always check what the hatch or port maker recommends for your model.

Remove the fasteners and lift the frame carefully, working a thin blade around the edge. Clean the deck and the frame of every trace of old sealant. Check the cut edge of the opening: if you see bare core (wood or balsa), seal it with epoxy before reinstalling (see the deck hardware guide). Dry-fit, mask around the frame, bed it with the recommended sealant or butyl, and tighten the fasteners evenly a little at a time in a criss-cross pattern until you see an even squeeze-out all around. Do not overtighten; a warped frame will not seal.

Measure the original pane carefully before buying plastic. SAIL's advice:

• Acrylic is usually the best choice for fixed ports: clearer, harder and cheaper than polycarbonate. Cast acrylic is a little better than extruded.
• Polycarbonate is tougher against impact but scratches easily and yellows in the sun unless it is a UV-treated grade.
• Leave room for growth: a 2-foot pane can grow by close to 1/8 inch from winter to summer, so it must not fit tightly in the frame.
• Keep the protective film on the plastic until it is installed.

If you drill holes in a surface-mounted lens, Practical Sailor says to make them slightly oversize and never countersink them, then seal the fasteners. A plastic shop can cut a new pane from your old one or a template.

Trim squeeze-out with a fresh razor blade once the sealant has set, peel the tape and remove the film. Let it cure for the full time on the label, then repeat the hose test from step 1 before putting interior trim back.

Rinse hatches and ports with fresh water after saltwater trips, keep the gasket clean, and work the latches so they do not seize. Log the job and the products used in BoatMend.