Easy DIY Boat Porthole Covers

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DIYing covers for your boat’s portholes (also called portlights) is an easy way to keep the cabin cool and comfortable while ensuring privacy. This cover pairs tough insulation material with eye-catching upholstery fabric for the perfect fusion of decoration and function. This simple cover tucks into the frame around the portlight screen — no fasteners needed. And best of all, it’s so easy that even a beginner DIYer can sew it! Dive into this blog to make porthole covers for your vessel.
Video Chapters:
  • Patterning Portlight – 0:33 min.
  • Cutting Thermozite Thermal-Acoustic Insulation – 2:10 min.
  • Sewing Decorative Face Fabric On – 3:01 min.
  • Using Hotknife to Trim Face Fabric – 4:58 min.
  • Installing Portlight Cover – 5:22 min.
Materials List:
  • Sailrite® Patterning Material 60" – #126150
  • Seamstick 1/4" Basting Tape for Canvas & Upholstery (36 yds.) – #122065
  • Thermozite Thermal-Acoustic Insulation 48" – #103153
  • Outdura® Rumor Midnight 54" Upholstery Fabric (6672) – #124489
  • Tex 70 (V-69) Navy UV Bonded Polyester Thread 4 oz. (1,350 yds.) – #106002
Tools List:
  • Sailrite® Clear Acrylic Ruler 6" x 24" –  #102400
  • Gingher® 8" Scissors Right Handed – #19104
  • Sailrite® Ultrafeed® LSZ Walking Foot Sewing Machine (110V) – #311602
  • Sailrite® Ultrafeed® Industrial Sewing Table – #120934
  • Sailrite® Edge Cordless Hotknife 18V Package – #122177
  • Precision Cutting Blade & Foot for Edge Hotknife – #125495
  • Marker, Masking Tape
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The inside (left) and outside (right) of our dual-layer boat portlight covers.

Our porthole cover is made of two layers of material. The first layer is Thermozite insulation. The second layer is a piece of the Outdura® upholstery fabric we used to redo the cushions and pillows in our boat cabin. We used the upholstery fabric to not only tie into the boat’s updated décor, but also to use up leftover fabric. If you have scrap upholstery fabric stashed away in your workshop, why not use it as the decorative layer of your marine window shades? It’s an easy and inexpensive way to customize your boat’s interior décor while reducing fabric waste. 

Despite its light weight, Thermozite Thermal-Acoustic Insulation packs a punch in heat resistance. A 1/4" layer of polyester fiber mitigates heat escaping from the cabin, while a reinforced foil layer deflects light to prevent outside heat from making its way in. The polyester fiber layer is made of 100% post-consumer recycled plastic, so you can feel good about using this effective heat barrier for your DIYs. 

Our tutorial video demonstrates just one way to make a boat window cover. If the portholes on your boat are different from the ones in the video, don’t worry. Just follow the steps we recommend to create custom covers to perfectly fit your boat's portholes. Watch the video above to learn how quick and easy it is to make a cover for every porthole window on your boat!

This project is part of our Seaward 32RK Project Series. We overhauled a Seaward sailboat from bow to stern. In addition to these boat window shades, we revamped the boat’s upholstery, made new sail and instrument covers, added a hatch canopy wind scoop, and much more! Whether you want to redo your entire boat or just update a project or two, you don’t want to miss this exciting DIY series.

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