well, i solved part of the mystery. I closed the back hatch, plugged the scupper holes and put the hose in the back where the bait tank would be.
10 minutes later i had about an inch of water in the boat!
So....there's that. Guess i will need a new gasket or something...
I will do the air hose trick too just to see if there is anything else, but Ocham's Razor says I may have found the problem. Anybody fixed a leaky back hatch? Time to go search the "share your innovation" thread....