Somebody in the history
of the boat made an alteration that ended up with your stuffing box right up against the engine
flange. Boats are not built that way - there should always be enough room between the stuffing box and the engine
flange to back the stuffing box nut/cap off and replace the packing.
- - Try to find out what was changed and change it back to the original configuration. Maybe the engine was moved aft due to worn out engine mount holes - or - a different transmission
was installed that was longer - or - - - - something strange was done.
Photos would great help in determining what was done and how to correct the problem.