Here is the new self draining scupper.
Assembly time about 20 minutes per scupper.
Cost: (2) siphons from Home Depot for about $3.00 each + shipping. (1) bag of 8 mm polypropylene balls (50 count smallest I could get) at $3.00 + shipping. (1) stainless steel mesh kitchen strainer about $3.00 at Target. (1) tube silicone adhesive $3.97 at home depot.
Cut at blue marks
The flapper and housing
cut mesh off strainer have the balls & glue ready
Cut mesh to fit and insert the balls into the cavity (flapper side of valve)
One housing held 3 balls and the other only would hold two balls. I may have cut it a little shorter at the hose or it was a manufacturing inconsistency. Two should work as well as 3.
apply bead of silicone glue around edge (careful not to get it inside)
Press screen in place and add small amount of silicone on top
Finished scupper drain
Apply a bead of silicone around the scupper and insert into underside of the seat drain scupper hole. Finish off filling around it with silicone.
Water test will be tomorrow once silicone has set overnight. The valves worked in the sink. The balls kept the flapper closed and opened and drained when when water was added above. There was no water returning past the closed valve.
Anxious to give it an open water trial.