Does your cockpit self drain? What type of cockpit drain do you have? Scuppers don't usually have an open and closed position. They may have a flap to restrict flow into the cockpit but they are open to allow drainage. The drains are typically above, or close to above the waterline. I had a centerboard boat which had cockpit bailers which when open at boat speed, would drain incidental water. Unfortunately, despite my best efforts, they would leak when the boat was at rest. - leading to sinking.
Finally I put fiberglass tape with epoxy over them and ended the problem. A well designed plastic container with a sharp corner did as good a job of removing incidental water and never caused concern about sinking the boat.