What rubber hose, the stuffing box hose or do you have a dripless seal? You need about six inches between the end of the shaft and the coupler to get the stuffing box off and then the hose if that is what has split. Hardest part is getting the shaft out of the coupler and MaineSail's site shows how to do that I think. Then you can slide the stuffing box and hose forward quickly and stuff rags around the shaft at the stern tube. But you need six inches between the prop and rudder to get the shaft back far enough. Then slide the box and hose off and install the new one. Like has been said, much easier out of the water. Cheap as I am I would try it at the dock first.
Just noticed that you have an H30. There might not be six inches between the end of the stern tube and the coupler.