I wonder about the procedure for replacing the packing. I would assume that once the boat is run for a bit, the packing will "settle in" and the nut will need to be tightened again? Kind of like when installing headers on a car: after installing them, the heat cycle can loosen the bolts a bit and after like 50 miles, they need to be tighened again. I am not sure, as I have never replaced my packing (560 hours on the original and only tigthened the nut once) but it it is just a theory.