My 1978 E27 also has four fixed ports. I have just purchased this boat and noticed the port over the galley was leaking. I was able to unscrew the inside screws, without stripping any, at which point the interior metal frame easily came off. Next l pushed on the port from several spots using light to moderate pressure and was, after about five minutes, able to break the silicon seal that holds the port fast to the outside cabin. The port came off easily, l cleaned all surfaces and applied new silicon sealant. Then realigned the port in the opening. This is where you should have two people. One outside to hold the port centered in the (very tight) opening clearence while another person inside installs the metal frame and screws it in place. So far the port has not leaked. My plans are to do this same task to all the ports this year before anymore leaks begin. I hope this helps you.
Chuck
E27/Scherzo