[willy]

Hey Air I know it may not be the mariner best way of doing things but I had the same problem with a full tank and a couple of super models aboard as you rock back in forth water would come into the scuppers, and because my floor is so level with the water line and the curve of the drain hose that water would not flow back out fast enough until I started moving.
I plug them! just those simple toggle end adjustable types you use for the drain plug in smaller aluminum boats. I put them in before I launch and if I have any water come in from fighting fish or swimming super models I just wait until I am in gear and moving forward and pull one or the both as needed to drain the little bit of water that gets in.
Of course if I am in some nasty snotty seas or something I would just pull them and leave open.
Works great