How to Replace Boat Windows

A broken or leaky window on a boat is much like a broken window in your house: there's an opening where there is not supposed to be one. Replacing the window on a boat is also much like replacing a window in your home in that boat windows come in standard sized. Unlike your home, though, your boat moves and the window openings on boats are rarely standard. This means that to fit properly, boat windows need extra care in installation secure mounting surface and a specialized two-part frame so that they don't rattle like a table with uneven legs every time you take on a wave.

Removing the Old Window

Remove the old window from your boat by using a flat screwdriver to gently pry the trim from around the interior side of the window. Unscrew the interior mounting frame and, with the assistance of a friend, lift the old window out of the window opening.

Prepare the opening for the installation of the new window by removing the shims from the old window and stripping any sealant tape or caulk from the wall. If the shims are in good condition, retain them and reuse them with the new window if possible. If the new window includes sealant tape to use between the exterior of the wall and the frame of your new window,

Check the Fit before Installing the Interior Frame

Lift the new window unit into place and check its fit in the opening. Like the windows in your home, it won't be a perfect fit in the opening and, quite likely, will need to have shims placed under it to center it in the opening. Since your boat will be moving up and down as it rides over waves, shims will be needed on the top and sides as well.

Put the interior window frame in place and hold the frame in place temporarily by screwing one of mounting screws provided with the window through the hole in the center of the bottom rail of the interior frame and one through the hole in the top of the window frame. Visually inspect the placement of the sealing tape under the exterior part of the frame to insure a good seal will result when the window is fully installed.

The Finished Window with the Interior Frame Installed

Secure the window tightly with the mounting screws and test the water-tightness of the window by wetting down the exterior of the boat at that window. Go inside the cabin and look for water coming through or around the frame; if there is none, reinstall the interior trim. If there is a small leak, apply caulking where needed.


  • When you remove the old window, set it off of the boat completely. Leaving the old window on deck while you're installing the new window creates a tripping hazard at best; at the worst, someone will step through the old window and take a trip to the emergency room with a bad gash on their leg.


  • Leaks will most likely be seen at the top or forward side of the frame, since water running down the exterior of the wall will infiltrate at the top of the frame and water splashing while the boat is underway will gain entry as it hits the front of the frame.


About the Author

Will Charpentier is a writer who specializes in boating and maritime subjects. A retired ship captain, Charpentier holds a doctorate in applied ocean science and engineering. He is also a certified marine technician and the author of a popular text on writing local history.