Sorry it's an 18ft. Marada ski boat with a I/O v6 mercruiser and it's fiberglass. The boat mechanic looked it over and didn't see anything and said he has never heard of that.
Possible that when pulling the tube..the load on the transom is causing some flexing? Opening a unseen crack when not under strain? Perhaps under the load you are leaking at the I/O housing?
How much water are we talking about?
It's filling all the way up into the floor of the boat in a matter of 15 to 20 minutes. The tube hooks on well above the water line. Is there any way to find this crack while the boats out of water?