cockpit scuppers 20 SF20

[Robert Fowler]

I am having a 1974 SF20 completely restored including new deck and transom. Prior to the restoration, I was having a problem with water entering the cockpit via the thru hull scuppers when anyone placed his weight aft of the helm. The height of the cockpit deck (sole) is barely above the waterline. I found it necessary to insert plugs into the scuppers when the boat was idle and would remove them when on plane to let the water out. With the restoration I have directed the mechanics to raise the deck 1 inch in an effort to help eliminate the water problem.

I have a question regarding the method I should use in replacing the scuppers. The existing and original design exits the scuppers directly down thru the bottom of the hull. I notice that new models exist through the transom and have a backkflow preventer "flap" on the exist fittings. I also notice that the location of the exiting scuppers is below the water line.

I am leaning toward changing the original design which goes straight down and thru the hull to one that exits through the transom. A question is whether water will exit through this scupper with the backflow flap substantially below the water line. Will the pressure from the water outside exceed the pressure from water trying to exit from inside and thus prevent drainage when the boat is idle?

I will very much appreciate anyone's ideas on this subject for my concern is that after completing this rather massive reconstruction, water still enters the boat through the scuppers.

Thank you