Is this fibreglass?
As Delmarrey suggested, they have to be a port designed to take that sort of pounding. Remember, one cubic metre of water
is a Tonne. Then throw that against the hull at speed. It is quite an impact. They are available though, and it can be done. I would suggest you talk to manufacturers of ports
and see what type they suggest, NOT to a supplier that will sell you his flavour of the month. The manufacturer could probably help further with installation advice as well.
My advice is, you may want a yard to carry this out if you are a novice
at glass work
. What you will have to do, is build up the area around the edge of the port, to stop flexing and allow greater holding power with either bolts or screws, as You will most likely find the hull thin at the area you wish to mount the port.