Hi Shucky
I took the liberty of making some notes to label part names on your photo. You ski has the unusual drive shaft with a nut, I have not found a correct drawing or parts list for that one but here are the drawing and part list for the 2008 GTI SE 155, unfortunately it's not as yours is... Yeah, lucky (not), I know.....
Looking at your photo there is a missing worm clamp for holding the carbon ring, you didn't put one on there to replace the broken one?
This is how I think your system works, although I haven't seen it before directly.
Okay, so inside the bellows there is a carbon ring (like a donut) that carbon piece is held in position by a stainless steel worm clamp around the outside of the bellows. But, this worm clamp is missing (I think it broke and fell off?).
The drive shaft attached to the engine spins as the engine is running, and it goes through the bellows and out through the transom to spin the jet pump impeller.
But a seal is necessary to keep water from leaking up from the underside of the hull where the drive shaft exits to reach the impeller.
The nut you have on the drive shaft has a stainless steel flange that makes 1/2 of the water seal.
The rubber bellows holds a carbon ring (like a donut) tight up against the flange of the stainless steel nut, this makes the other 1/2 of the water seal.
The drive shaft spins and the nut spins along with the drive shaft, while the carbon ring inside the rubber bellows doesn't spin and the carbon ring is pressed tight up against the flange of the nut as the nut spins this makes the the water-tight seal.
So if the clamp that holds the carbon ring is missing, water can leak between the bellows and carbon ring. You must have this clamp in place to avoid leaking.
If the carbon ring inside the rubber bellows is damaged or out of position, it might not seal flatly up against the stainless steel flange of the nut to make the seal thus, water can leak inward between the carbon ring and flange of the nut.
I think where you drew the arrow has nothing to do with the water leaking, that's my best guess. It seems like the leak should be in the vicinity of the carbon ring?