How can I change this (cockpit drain)?

[Seriola Dumerili]

Hello everibody,
My GW Offshore 24 have so little space arround the drain holes. There is just a small hatch about 4 inches diameter. How on earth can I change the white plastic fitting. Is there any tool for this job? Tips wellcome
I have attached some pictures

 

[derx2]

couple of ideas-

you could remove the frame of the 4" inspection port from the hull, this will give you another 1" of room to stick your arm though.

you may have to chip out or remove some foam on the backside of the floor drain to install the new drain.

to remove the floor drains (like the ones you have) on my boat, I did not bother trying to unscrew them. I took a hole saw or forstner bit that was a little bigger than the hole in the drain, drilled them out from the top. I was careful to stop drilling before I reached the gel coat of the boat hull. Then I broke the old floor drain by cracking it

you may have to install another 4 or 6" inspection port on the bulkhead next to the existing one, or enlarge your 4" one to a 6"

Could you access that part of the hull sides by removing a panel from in the cabin area?

 

[Seriola Dumerili]

from the cabin side there is a bulkhead between, so I have no access.
removed the frame. asked my 13 yr old daughter for help. she assembled in place all pieces except the tube :wow
I think that in newer GW models this is much simpler job. I am happy again, thank you for your help