Make a Porthole

  • 2-6 hours
  • Intermediate
  • 40-1,500

A porthole is a sealed window in the hull of a boat that allows light inside an otherwise enclosed and dark space. Portholes are a common feature amongst boats with interior cabins. Adding a porthole to your boat is not a difficult process, but one in which you must be very careful. A porthole that isn't sealed or installed properly can leak water into the cabin and cause a variety of other problems as well. Read on for a set of instructions on how to install a porthole in your boat.

Step 1 - Select Materials

The first step toward installing porthole is deciding on the material for the window itself. While many older boats use shatterproof glass, in recent years, most manufacturers have turned to fiberglass and plastic for the window material. These products offer good visibility and excellent protection against damage. Creating your own window piece is a difficult process that is not possible without specialized equipment and knowledge of glassblowing or plastics. In fact, it is recommended that you purchase the window material itself from a boating store.

In addition to the window material itself, you'll need the following equipment:

  • Sealant appropriate to your boat's design and construction material
  • Drill
  • Hammer and nails
  • Saw, per the instructions for the window itself

Step 2 - Clear the Opening

Decide where you will place your porthole, keeping in mind that the window itself needs to match the curvature of the boat. Following the manufacturer's instructions carefully, cut away the wood or plastic frame of the boat to leave room for the porthole itself. If your cabin shell comes in multiple pieces, you may find it easier to partially dismantle that portion of the boat before setting the porthole frame.

Step 3 - Set the Frame on the Outside and Inside

The strongest portholes are framed on both the exterior and the interior. Most portholes that are designed to open have latches on the outside portion of the boat, although you can reconfigure this if you'd like. The window itself should come with a frame or instructions on building a frame. If you do need to make your own frame, use plywood. Be aware that you may need to paint the frame later on in order to match the color of the boat itself.

While a hammer and nails may be helpful in securing the frame to the exterior and interior sides of the cabin, a through bolt is more secure over the long term. If the porthole kit did not come complete with through bolts, purchase them at any hardware store so that you can attach the porthole frame by these means.

Step 4 - Install the Window and Seal

Following the installation instructions of the manufacturer, complete your porthole by installing the window itself into the frame. The single most important step of the completion process is properly sealing the window so that no water can enter the boat. Ensure that there are no gaps whatsoever between the porthole window and the frame of the boat itself. After installation and sealing you may paint the frame of the porthole if you wish.