Outdoor Renovation

How To Repair The Seal On Acrylic Boat Windows


Window seals on boats are generally not protected from damage by UV radiation resulting in them breaking down and cracking overtime.

When replacing your boat window seals you want to ensure you are using a product with excellent UV resistance.

Selleys MarineFlex is a high performance adhesive sealant that can be used on boats, pools & spas^ (in fresh, salt and chlorinated water) where you need a waterproof seal, even under water*- it can be applied and will cure under water. Compared to traditional polyurethanes it provides a more durable seal with superior UV resistance.

To begin with, you want to remove the old sealant, here’s how –

  1. Cut away at the sealant using a sharp blade (be careful not to cut yourself or damage the window)
  2. Ensure the surfaces are completely dry
  3. If a Silicone has previously been used you can fully remove it with Selleys Silicone Remover, apply it by layering it about 3mm high. Allow 2-4 hours for thin be of sealant – it can be significantly longer if the silicone is not cut back first and may require multiple applications. It is important to make sure the remover does not dry out while you wait the couple of hours for it to soften the silicone
  4. Once it is softened, you can clean the silicone up with methylated spirits- do not use water
  5. For old polyurethane sealants you are best cutting as much as possible and removing the rest with a light sand

Once the old sealant has been removed -

  1. Lightly sand the surfaces that the new Selleys MarineFlex seal will be applied to and then wipe clear with mineral turpentine or white spirits
  2. Cut cartridge tip, fit nozzle and cut to size, then insert into the caulking gun
  3. Apply the sealant around the window
  4. Tool off excess product with a cloth (if underwater) or soapy solution before skinning occurs
  5. See technical data sheet for more information

Important Information:
#Not suitable for Polypropylene, Polyethylene or Polytetrafluoeoethylene
*Critical seals/repairs underwater should be regularly checked & repaired if required.
^Fibreglass, polycarbonate and Perspex should be lightly sanded and wiped with turps prior to product application