We had a wetjet growing up and my dad still has one, I’m pretty sure that stock they dump all water through the exhaust. Not all at the stinger, there is a cast aluminum exhaust elbow next to the jetpump where it dumps the remaining water. Anyways, is it possible that the jacketed section of the pipe is clogged with lake trash or something forcing all the water through the tiny holes inside the pipe designed to cool the chamber? You could try testing it with a water hose just barely turn the hose on. It would be best to test it off of the motor, if you leave the water running and the engine off you will end up with water in the motor once the water level in the manifold reaches exhaust port height. I have seen little sticks plug the cooling lines before and flowing water backwards through the system will often push it out into the jet pump. If you have a hose the diameter of your pisser and know what it looks like normally ridding then kinda whip the hose around and adjust water pressure until you get the waterhose to looks like the pressure coming from the ski. (A non scientific way to get close on water hose pressure)