how to access the toilet valve at sea

Apr 24, 2013
25
HUNTER 33 NOUMEA
The sea access valve, the one that allows the toilets to be evacuated directly into the sea, is located behind the black water tank. I need to change the pipe that goes from the Y selection valve to the direct sea outlet valve. How should I do this?
Do I need to make a hole in the transom to have easier access?
User of a HUNTER 33 from 2005 and later, have you had this problem and how did you solve it?

Thank you for your answers