Having a difficult time picturing exactly what you mean when you say you have "a leak under the aft end of the prop seal".
Is it the hose coming off the thru hull
going to the stuffing box that is leaking? (If not, could you show us a pic of the leak). If it is the rubber hose, would take it apart during a haul out
and inspect the thru hull
and hose. This hose is typically a small section of exhaust
hose and would replace it. It is more of a pita to do this and why the PO probably put a tube of caulk on it instead of doing it correctly.
In general, you will need to uncouple the shaft from the motor
, remove the coupler, then push the shaft back enough to slide the stuffing box and hose off the forward end of the shaft. Measure the thru hull
carefully to purchase
the correct size rubber exhaust
hose. Can change the stuffing box packing and replace the hose clamps w/good quality SS clamps at this time also.
While you are at it, you may as well change the cutlass bearing and then you are done for a while.