How to Repair and Maintain Deck Hatches and Portlights

How to Guides

a young girl comes out of the deck hatch on a boat

There are plenty of small maintenance and repair jobs that need to be done on your boat. Over the course of a year you could save yourself a small fortune by doing some of the work yourself rather than paying someone to do it for you.

Some jobs are complex and worth paying for, but small jobs like repairing deck hatches and portlights could be doable with some basic DIY skills and a little research.


Glass vs Acrylic or Polycarbonate

Plastic portlight lenses are nearly always made from see-through acrylic (PMMA). Common brand names include Crylux, Plexiglas, Acrylite, Lucite, and Perspex. Portlight lenses can also be made of tempered glass, which has better longevity and is also easier to clean.  However glass is brittle, which means it should only be installed in a rigid frame. This means it is unsuitable for fixed portlights, because even portlights with metal frames flex to the contour of the side of the cabin.

Plastic hatch lenses are often made from see-through polycarbonate (PC) such as the Lexan or Makrolon brands. Both acrylic and polycarbonate have pros and cons.  Acrylic is shinier and cheaper than polycarb but easier to crack. Polycarb is more resistant to impact but scratches more easily than acrylic. Both of them are lighter than untempered glass, with acrylic being 4 to 8 times stronger than untempered glass. Polycarb is around 200 times stronger than untempered glass.

Acrylic hatch or portlight lenses don’t last forever. Over time they become faded, crazed, hazy and stop sealing. They not only make the boat look tired, but when the seals also don’t work, it makes being below deck unpleasant. Everyone notices the hatch when they go below deck. Even if you restored or replaced every other part on your boat and neglected to revive the hatch, it will still look like an old, tired boat.

A new acrylic lens can make all the difference to the hatch if the old material is well past its use by date, but in a lot of cases the acrylic can be restored to a beautiful finish. Gather your parts and tools and tackle the job.

Restoring the Acrylic

The biggest problem with acrylic lenses is crazing. Once see-through acrylic turns opaque and ugly with age but you can bring it back to life. The My Sailing website details how yacht owner David Bowden restored an acrylic hatch that looked unrecoverable from crazing. David worked on the acrylic windows of his catamaran in 2012 and, years later, the windows are still in good condition. He not only enjoys a better view, but he has saved himself the hassle and expense of replacing the hatch and windows. He concedes his technique won’t make the acrylic look brand new but you need to look hard to see the imperfections.

By removing 0.5 mm of the acrylic you can remove surface crazing. If it’s bad, you may need to remove up to 1mm. It only takes around an hour to revive an acrylic hatch or window (portlight).                   

1.    Use a 150mm random orbital sander and a 40 grit paper. Move the sander in even sweeps in alternate directions. Wait until the craze disappears before moving to a finer grit paper to polish.

2.    Start with 60 then move to 80, 120, 180 and finish on 350 grit paper.

3.    Check the underside of the acrylic in case light crazing has occurred and if so treat with a fine paper.

4.    Use a polishing and finishing pad as a final step.

5.    Fit the acrylic back into the mounting frame.

David recommends using a regular protectant if a full sun protectant isn’t available. The sun’s rays, dirt and chemicals cause most of the damage to acrylic, so avoid cleaning with harsh solvents such as benzene or ammonia. Be wary about using plastic mesh sunscreens. A fabric cover is a better option than plastic.

Replacing the Gasket

There is nothing worse than storing your gear under a hatch only to find it wet from spray or wash down. To make your hatch watertight again, try replacing the seal/gasket.

Order the correct size gasket seal for your hatch. Once it has arrived, you can get to work stripping out the old and replacing with the new.

1.     Pull out the old gasket and use a narrow chisel or knife to remove all the old adhesive.

2.     Use Isopropyl Alcohol on a rag to wipe over the gasket area.

3.     Pull the backing cover off the end of your new gasket and starting at a hinge, install around the perimeter.

4.     Once you have covered the edge, carefully cut to create a butt joint.

5.     Next take a new tube of super glue and cement the butt joint, being careful not to get any on the lens then allow to set for five minutes.

6.     Apply pressure to the entire gasket to ensure the tape adheres.

Use a marine silicone lubricant to extend the life of your gaskets, weather stripping and seals.  

Replacing and Resealing a Portlight

Just like hatches, portlights will give away an old girl’s age. Replace or maintain them to keep your vessel looking good.

Replacing the Portlight

If you want to replace a portlight on an old boat, you may struggle to find a replacement one to fit the same aperture. You could be forced to install a bigger or different-shaped portlight. If you find a portlight that is slightly smaller than the gap left by the old light, fill it with plywood or foam skinned with fibreglass. However, there is a considerable amount of work with this option and, if not done well, it may leak in the future.

It may be worth ordering a custom-made portlight so it fills the aperture and saves you time. To ensure you get the size right, remove the old light and make a template for the manufacturer. Sailing Magazine show how to replace an old portlight with a new one here.

Resealing Portlights

A common problem on older boats are leaks around or through the portlights. The leaks can cause plywood to warp and buckle. Much of the damage may not be obvious at first so don’t leave a leaking portlight unrepaired.

Always use a
marine grade silicone sealant. Plastic leaks oil over time so a good quality silicone sealant is your best line of defence against future water leaks. You can read more about the types of sealants available here.

1.    On the outside of the boat cut the old caulking by prying the frame off the boat with a putty knife. If the frame doesn’t budge, try a small electric cutting tool to cut through the caulking before prying off.

2.    Use a small sharp chisel to remove the remainder of the old silicone.

3.    Move inside the boat and pry the frames off.

4.    Use a scraper to remove all the old sealant off the frames. Remove any rough surfaces and contaminants from the edge of the hole in the hull.

5.    Use an acetone solvent to clean off any remaining contaminants. Always do a patch test of any solvents. Clean the portlight with solvent on a rag to ensure both surfaces are perfectly clean.

6.    Drill holes in the new trim.

7.    Slowly spread caulking around the portlight on the inside and outside edge.

8.    Put the screws in and use a scraper to remove the excess caulking that has escaped from under the light.

9.    Finally, clean up the last remaining residue with acetone.

You can watch a video of the process.

Keep your ageing boat looking good by repairing and restoring parts as they show signs of wear and tear. You will not only enjoy a great-looking boat but it will keep your boat functional.

If you have any queries about the materials you need to do these DIY jobs, give us a call on 1300 308 161 or contact us online for advice.

Category: How to Guides

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