Replacing Boat Window Seals: A Step-By-Step Guide

Replacing boat window seals can be a challenging task, but with the right tools and knowledge, it can be done successfully. The process involves removing the old seals, cleaning the surfaces, taking accurate measurements, and installing new seals to ensure a watertight fit. This is particularly important for boats with aluminium window frames, which are prone to leaking due to poor design and construction. When re-bedding the frames, it is crucial to use a non-hardening caulking or sealant that can accommodate movement without breaking the seal. Additionally, proper clamping and shimming techniques are essential to prevent leaks and ensure the window is securely held in place.

Measure window and panel thicknesses to get the right seal

When replacing boat window seals, it is essential to measure the window and panel thicknesses to ensure you get the right seal for a tight fit. Here's a step-by-step guide to help you through the process:

Step 1: Identify the Type of Window

Before taking any measurements, it is crucial to identify the type of window you have on your boat. Common types include fixed windows, windshields, and sliding windows. Knowing the specific type will help you determine the necessary measurements and the appropriate replacement.

Step 2: Gather the Right Tools

To measure the window and panel thicknesses accurately, you will need a few tools. A tape measure or a ruler will be essential for taking precise measurements in inches or meters. Make sure you have a notepad and a pen or pencil to jot down the measurements as you go.

Step 3: Measure the Window Width

Start by measuring the width of your boat window. Place the tape measure or ruler along the bottom edge of the window and extend it from one side to the other. Note down the measurement, as this will help you determine the precise thickness of the rubber seal you will need.

Step 4: Measure the Window Thickness

Next, you'll want to measure the thickness of the window itself. Place your tape measure or ruler on the edge of the window, and measure from the outside surface to the inside surface. Make sure to take measurements at multiple points along the window, as the thickness may vary slightly. Record these measurements, as they will be crucial for selecting the correct seal.

Step 5: Measure the Panel Thickness

In addition to the window thickness, you'll also need to measure the thickness of the panel where the window will be installed. Simply use your tape measure or ruler to determine the thickness of the panel at the desired installation point. Take measurements at several points to account for any slight variations.

Step 6: Compare Measurements and Select the Right Seal

Now that you have accurate measurements for both the window and the panel, you can select the appropriate seal. It is crucial to choose a seal that matches the thickness of your window and panel to ensure a tight and secure fit. Compare your measurements to the specifications provided by the seal manufacturer or supplier.

Remember, taking precise measurements is vital to ensure a successful boat window seal replacement. By following these steps and paying attention to detail, you'll be able to select the right seal and create a tight and long-lasting installation.

Remove the window and clean the frame

To remove the window and clean the frame, follow these steps:

Firstly, it is important to take accurate measurements before removing the window. Measure the width of the window to get the precise thickness of the rubber. The thickness of the window and panel should also be measured to ensure a tight fit.

Next, if your window has a frame, carefully cut any sealant internally with a sharp blade at the window/frame moulding interface. If your window does not have a frame, you will need to remove the rubber weather stripping that attaches to the pilothouse and window.

If your window has a frame, go around the exterior of the frame edge with a stripping/filler knife, cutting into the sealant. This cut should be shallow at first, but become progressively deeper as you work around the frame. You can also use a small garrote made of piano wire, poked through the seal and used as a saw to cut through.

If your window does not have a frame, you will need to remove the locking strip from the weather stripping. There should be a flap on the outside of the window that needs to be pulled up, which locks the window in place. A hook, either metal or plastic, can be slipped under where the two ends meet and pulled up.

Once you have cut through the sealant, you can start to remove the window. You may need to use a wire to "unzip" the seal, with someone pushing on the window from the inside. Alternatively, you can use duct tape to create a loop from the hull to the window frame, which will prevent a crash when the window pops out.

Now that the window is removed, you can start to clean the frame. If your window has a frame, you will need to dismantle it before cleaning. If your frame is in two halves, you will need to remove the fishplates – thin strips of metal located in the bed of the channel held by screws through the frame. Carefully clamp the frame and remove the screws, taking care not to damage the frame or break the glass. Once the frame is in two halves, separate them and clean out the old butyl sealant from the channel using a screwdriver, plastic scrapers and a scouring pad, along with white spirit or a similar solvent.

If your window does not have a frame, you can move straight to cleaning the window aperture in the hull. Use a variety of tools, such as scrapers and solvents, to clean the aperture thoroughly.

Once the frame and window aperture are clean, you are ready to start reassembling the window.

Clean the window and its edges

Before you start the process of replacing your boat window seals, it is important to clean the window and its edges thoroughly. This will ensure that no dirt or debris gets trapped under the new seal, which could compromise the seal's integrity and reduce its lifespan. Here is a step-by-step guide to cleaning the window and its edges:

Inspect the window for any damage: Before you begin cleaning, carefully inspect the window for any tears, deep scratches, or holes. If there is significant damage, it may be best to replace the window altogether. Minor scratches or imperfections can be addressed during the cleaning process.

Remove any debris and dust: Start by removing any large pieces of debris or dust from the window and its edges. You can use a soft-bristled brush or a microfiber cloth to gently wipe away any loose particles. Be thorough in this step, as any remaining debris can scratch the window during the cleaning process.

Wash the window with a mild soap solution: Fill a bucket with warm water and add a mild soap or a boat cleaner designed for vinyl or acrylic windows. Dip a clean microfiber cloth into the soapy water and wring it out well. Gently wipe down the window and its edges with the damp cloth, ensuring you get into all the nooks and crannies. Avoid using abrasive soaps or cleaners, as these can damage the window surface.

Rinse the window with fresh water: After washing the window, rinse it thoroughly with fresh water to remove any soap residue. You can use a hose with a gentle spray nozzle, or fill a clean bucket with fresh water and use a second microfiber cloth to wipe away the soap. Ensure that all soap residue is removed, as it can leave streaks or attract dirt if not thoroughly rinsed.

Dry the window and edges: Using a clean, soft cloth or microfiber towel, gently wipe down the window and its edges to dry them completely. Be sure to use a gentle touch to avoid scratching the window surface. You can also use compressed air or a squeegee to speed up the drying process, ensuring there are no water streaks or spots left behind.

Restore and polish the window: Once the window is thoroughly cleaned and dried, you can apply a vinyl window restoration formula using an applicator pad. Be sure to consult your boat manufacturer's recommendations for the best restoration products to use. After restoring, polish the window using a foam applicator pad and a product specifically designed for boat windows.

Treat the window with a protective wax: Finally, treat the window with a boat-approved window wax to protect the surface and maintain its shine. This will help repel water and reduce the buildup of dirt and dust, making future cleaning easier.

By following these steps, you will ensure that your boat window and its edges are clean and ready for the new seal installation. Remember to always use products specifically designed for boat windows and to consult your boat manufacturer's recommendations whenever possible.

Prepare the frame for installation

Before installing the new boat window seal, it is important to thoroughly clean and prepare the frame. Here are the steps you should follow:

• Remove the old window and seal: Carefully take out the window and old seal or rubber gasket. This may require the use of a screwdriver or specialised tools like a garrote made from piano wire. Be gentle to avoid damaging the window or the surrounding structure.
• Clean the frame and glass: Use a combination of solvents such as toluene, lacquer thinner, acetone, white spirit, and alcohol to clean all mating surfaces. Ensure that you remove all traces of old bedding, corrosion, or crud. Pay special attention to the window channel, as it tends to accumulate dirt and corrosion. You can use tools like old screwdrivers and plastic scrapers, along with the solvents, to clean effectively.
• Prepare the glass for reinstallation: Clean the edges of the glass with an alcohol-based glass cleaner, such as Windex. Ensure that the glass is free of any residue or impurities before proceeding to the next step.
• Apply primer: Use a small brush to apply a primer to the inside and outside faces of the frame and glass interface. Allow the primer to set for at least 30 minutes but no more than 8 hours.
• Create a chocking diagram: As a reference, create a diagram that illustrates the placement of rubber chocks or spacers between the glass and the frame. This will ensure that the glass is securely held in place and has sufficient movement within the frame.
• Insert rubber chocks: Cut rubber chocks or spacers to the appropriate size and insert them into the channel around the glass perimeter. This will provide support for the glass and prevent it from moving excessively.
• Apply butyl sealant: Wear gloves and mix equal quantities of the black and white components of the two-pack butyl sealant by twisting and kneading until a consistent black colour is achieved. Firmly insert the butyl into the frame, using a strong rotating action to maximise pressure. Ensure that the butyl fills the bottom channel of the frame.
• Reinstall the glass: Press the glass into the frame, creating a new void around the perimeter. Insert the internal vertical face chocking rubber at intervals of roughly 75-125mm to support the glass. Make sure the chocks are pressed below the frame edge but still provide coverage for the butyl glazing sealant.
• Chamfer the edges: Use a knife or any convenient tool to smooth and radius the edges of the butyl sealant, creating a clean finish.
• Clamp the frame: If necessary, use clamps to realign the frame to its original dimensions, referring to the stencil or measurements taken earlier. This ensures that the frame is not distorted and aligns correctly with the window opening.
• Prepare the window opening: Clean the hull window opening thoroughly, using tools and solvents to remove any dirt or residue. Make sure the opening is free of corrosion and crud, just like the frame and glass.
• Apply bedding compound: Cut the nozzle of the one-pack butyl sealant at a 45-degree angle. Apply a 6-7mm bead of bedding compound on the inside of the window flange, forming a doughnut shape around the screw holes. This will create a seal between the window and the hull.
• Test fit the window: Present the window to the hull, ensuring it is the right way up, and gently press it against the hull. This will create a 'witness' line around the perimeter, indicating the points of contact.
• Insert screws: Carefully tighten the screws, working around the perimeter of the frame. Do not fully tighten the screws yet; just 'nip' them up for now. This will allow for any necessary adjustments and prevent excessive pressure on the butyl sealant.
• Trim and clean: After a few days, when the butyl sealant has hardened, use a scraper and white spirit to trim away any excess sealant and clean the frame. This will give it a neat and finished appearance.

Reinstall the window

Now that you have cleaned the window frames and the boat hull, it is time to reinstall the windows.

Firstly, check the fit of the window and alignment of screw holes in the hull opening. If your boat is like the Sadler 32, you may need to ease the hull window opening by a couple of millimetres to enable the frames to fit back in. You can do this with a tool made from a 10cm block of wood and some old aluminium tile trim.

If your windows have a slight curvature, you may want to avoid potential future leaks by incorporating small rubber spacers made from a material like Firestone EPDM roofing. Bed these in butyl sealant a day in advance of installation.

Next, prepare each frame for installation using a one-pack butyl sealant, which is non-setting and can be cleaned up with white spirit. Cut the nozzle at a 45-degree angle and apply a 6-7mm bead of bedding compound on the inside of the window flange in line with the screw holes. Form a doughnut shape around the screw holes themselves, and use a little more sealant if you are incorporating spacers.

Now, present the window to the hull the right way up and gently press it against the hull, which will create a 'witness' around the perimeter. Remove any initial sealant that appears in the screw holes in the frame, to avoid a hydraulic build-up of pressure. You may also wish to put a little sealant around the neck of the screw to ensure an effective seal.

Carefully tighten the screws, working around the perimeter of the frame. Do this in rotation several times until only a small gap remains between the hull and the frame. The butyl should not be squeezed out completely, or it will leak. Screws should only be 'nipped up', not fully tightened. Leave for a few days to harden, then trim using a scraper and white spirit.

And that's it! Your windows should now be watertight for another 25 years.

Frequently asked questions