It may seem strange but if you drive the boat with the plug out it will actually drain. ( No I did not see this on the three stooges) My dad used to do it on our boat which did not have a bilge to drain the rain water out. The water behind creates a vacuum if you are moving. And if that does not work, just drill more holes to let the water out...
Also keep in mind that if you blow a cooling hose you can pump even more gallons per minute into the boat by keeping the boat running.