Keeping water from comming up the drains

[RidgeRunner]

The clear scuppers with the pingpong ball mounted externally work well to eliminate the flow into the boat and are a nice upgrade. The ball acts like a check valve, it lets water out so long as the water level is below the scupper, when the stern dips under the water the ball floats up and seals the hole. These are more durable than they look but do require a bit of maintenance because debris such as sticks and leaves will prevent them from working properly. The maintenance is easy, grip the clear housing on the outside firmly and turn the housing 1/8 turn to remove clean and inspect.
Chances are the boat has some scuppers there already but they aren't working properly.