ball scuppers

[sidelock]

I purchased a pair of TH Flow-Max ball scuppers with the intention of installing them on my 18SF but when I submerged them in my kitchen sink to see how they work & how effective they are before I drill any holes in the transom , I could'nt get the ball to seat properly & block the opening no matter what angle I submerged them at. The ball keeps getting pushed up against the top of the clear housing but does'nt seat in its intended position. Has anyone used these particular scuppers ? Do they work differently when they are fastened to the transom ?