Replacing deck hatches with new plastic is not as difficult as you think, if you know how. Boat cleaners, sunlight, and pollutants gradually destroy these plastics and create clouds, making it hard to see through them. But, if you follow the simple steps below, you can have a professional hatch replacement done by you.

This job is best done on a sturdy surface off the boat. First, remove the hatch top from the deck frame, then remove the lens. This may take a couple of hours. Hopefully, the fasteners won’t be corroded and the nuts exposed so it will not be necessary to remove the cabin liner. You may need to replace the gasket if it is in poor shape. Cover the opening in the boat with plastic sheeting or some other device while working on the hatch in order to protect the interior.

Measuring (25") square and (3/8") thick, (these are example sizes - you will need to measure your own requirements) the replacement lens in grey Acrylic will cost approximately $100. The milling charges to cut and drill fastener holes is approximately $40. If you do not have the proper tools to fabricate plastic, (cutting and drilling) this job is best done by the supplier.

Follow these procedures for a leak-free hatch replacement lens. (A professional would budget 6 to 8 hours for this job and charge approximately $600 installed.)

Step A
Remove the original caulking from the groove in the hatch frame using a sharp chisel. Be careful not to nick the inside gasket. Removal could take a couple of hours depending on what compound was used. It is not necessary to remove all the compound, just the loose residue to make sure you get good adhesion. Sand lightly with 80 grit paper to remove loose bits and clean the groove with a whisk or vacuum.

Step B
Mask the frame edge. We suggest 3M 233 tape in 19mm (3/4") width for this job. Overlap each piece and extend the tape ends to provide a good grip later when removing it. Tape across corners, then with a sharp knife, single edge razor blade, "saw" the tape following the shape of the frame. Press tape down firmly. This will make sure the caulking won't run under the tape and you will get a straight, finished caulking line. If your hatch has a separate gasket, you should mask the outside and inside edges. If you have only an overlapping gasket that wraps around the frame, then any sealant that oozes out can be trimmed later.

Step C
Place the new lens on a protective surface (i.e. - bubble wrap) and remove the paper mask. Handle carefully as plastic can scratch very easily. A suggestion is to make sure you remove watches, rings, etc in order to make sure you do not scratch the lens. Determine front and back and put a piece of tape on the underside for reference. Mask the edge of the lens, using your thumb to feel the edge and align the tape. The neater you get it the straighter the finished edge. Trim the corner with a razor blade using a sawing action.

Step D
To caulk plastics we suggest using Sika and Sika primer, a construction-grade silicone available in black, clear or white. This product requires no preparation. It has a working time of one hour and cures overnight. Application can differ because of the gasket. Usually, you fill the groove with sealant and any excess oozes out onto the taped edges (see Step B). Instead, carefully caulk the outside frame edge so it just overlaps the bottom ledge. Fill in the gap from the top once the lens is placed. With a gloved finger, smooth the lumps and spread the sealant evenly. With mating the two surfaces, a good joint is usually the result.

Step E
Lay the lens in the frame, carefully checking the front and back positioning before putting into place. Centre the lens in the frame. The silicone has a working time of about 20 minutes at 10°C (50°F). You will have to move quickly with normal temperatures. Press lightly down, applying just enough pressure to seat the lens in the frame. If the hatch frame is bowed, you will need to weigh down the lens. We suggest a wooden block (or something similar) placed over a protective cloth in the centre of the lens. Then lay a batten across the block and clamp it to the frame.

Step F
Caulk the gap between the lens and frame edge. Apply pressure to squeeze the caulking into the gap and remove any air. Run a 1" putty knife along the tape to smooth the caulking. Hold the knife at an angle so it does not run off the masking tape. Often there is a height difference between the frame and the lens. When the lens is lower, run the knife flat along the frame edge, leaving a slight bevel up to the lens. Re-caulk any low spots or air pockets and level with the putty knife. If the hatch has a narrow gap, run a finger along the edge for a neater finish. Do not do this if the gap is wide or you will make a definite groove.

Step G
Remove the masking tape now. Do not wait until the silicone hardens or the tape may lift the silicone off. Start at the corners, pulling back the top tape layer on the frame. Now pull up the tape on the lens side, join the two and pull off both at the same time. This will prevent caulking strands from dropping off the tape onto the frame or lens. Angle the tapes back when pulling, not up, which may pull out the caulking or lift the lens. Wait until the sealant cures to remove any tape or sealant residue and scrape off with a razor blade. Hold the razor blade flat when trimming. To remove caulking off the lens, let it cure, then rub with your finger and it will roll off. Any uncured sealant can be removed with Varsol if needed. If it does leave a film, clean with a special plastic cleaner when the silicone is fully cured.

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