It is a '97 Marstrøm.

Thanks for all the advice. Actually, I do not want to drill a hole through both sides of the hull. I would try to complete the whole operation just from on side. This also also explains the somewhat strange shape of the plate; it is the largest plate that fits through the existing hole.

I assume that the new Marstrøm boats are already equipped with such a (or a similar) fitting. Does anybody know how these are attached to the hull ?

Thanks
Ceitzi