Can anyone help us?

We have a leak, but not through the porthole from outside in.

It would appear that the water is finding its way in to the salon via the porthole.

We want to take the porthole out so that we can reseal it.

We have removed all screws inside and out but it is holding fast without any leverage.

Are the more screws inside? Is it glued on?

Does anyone know. Any help offered is much appreciated.

French Knight