@Beachbummer , all points well-made. Don't disagree at all. I was just thinking the size of the scupper (allegedly cracked, so a 'crack', but even completely removed) is, what? a 1" hole or so? Not pumped, but certainly with water pressure behind it. Then you have the bilge with a 3/8" hole, actively pumped. Yes, the bilge loses. But in 5 min? That is a pretty short time period.
You may be completely right and it may just be the scupper. But, were it my boat, I would be checking for more. Worst case you don't find anything.
Totally agree on the alarm. I added a 2nd bilge pump, too (redundancy at least, double capacity at best). I should have put it in the lower bilge, which is the other thing I would say about the stock design: an alarm and relocating the pump down by the bilge plug so you didn't start pumping 40 gal of water behind...