Thanks for posting the picture. Weight and bracket are not the culprit. And yep, now I believe your Seacraft is really a fountain
. Bushwacker and Capt Chuck are right on. Whoever doctored that hull should stick to pottery
. The recessed pocket behind the wedge is effectively serving as a scoop slowing or diverting water right up you wazoo, err, scupper tube. I'll get a picture of what mine looks like tomorrow. The right angle at the back of the wedge Bushwacker mentioned separates the flow of water, maybe creating a pocket of air aft, allowing water to be sucked out. And the hull's straight line minimizes friction enabling the water to flow by with little impedance. The altered pocket you've shown us is definitely the root of your fountain.
It also appears the scupper tube is toast and the seal is gone so you'll probably have a saturated wood block that surrounds the tube which may be corrected like Bushwacker described in his scupper restoration. Whether you plug the tubes from above or not, I think you'll still be taking on water. Consider taking corrective action soon. Good luck.