This applies to both catalogue sizes supplied direct from Lewmar and custom sizes produced by Eagle Boat Windows.
The fitment is very similar, but the hinge pins on Mk3 are M5 where as those on the Mk2 are M4 meaning that the alloy mounts need to be switched to accommodate. Acrylic kits are supplied with suitable Mk3 mounts (for both hinge and catch) as standard.
However, there is a slight catch (if you'll excuse the pun), in that the mounts clip over the outer edge of the outer frame before being fixed in position with the single machine screw. This 'catch' thus applies to removal of the existing Mk2 mounts as well as their replacement with the Mk3 parts.
If your hull cut out is not tight, this may be a non-issue as you will have space to un/clip the mounts in situ. If the cut out is tight however, you have two options;
remove the whole port, switch the mounts/acrylic and rebed/refit to the hull - This is quite straight forward and an easy DIY job.
enlarge the cut out around the mounts using a suitable tool (eg Dremel or MultiTool) to allow the mount removal/replacement.
Which you choose (if needed) is up to you, but bear in mind your existing bedding compound will be at least 15 years old (Mk2 2000-2007) and may well benefit from upgrading. The outer frame flange is quite narrow (~12mm) and lends itself to bedding with (butyl) ARBO GZ tape (which we can supply in 12m rolls). Compared to traditional butyl 'goo' (eg ARBOmast BR bedding compound, we also supply), this is a no mess equivalent which will also ensure a 1mm seal remains all around the port.
For guidance on removing a window, see our other blog post on removing fixed pane windows (same principles apply).