My take is "it depends." If it's never been tightened after its initial install, you're
probably ok tightening it
a bit. You have to be careful, as over-tightening can wear grooves in the prop shaft and then you'll never get a good seal. I certainly wouldn't tighten it much. Ours, right now, dripping only rarely at rest and every 10 seconds or so under way, is still well less than hand-tightened. (I just snugged it down maybe 1/16th turn to try to reduce the drip rate a bit.)
We were lucky in this respect: Ours started dripping excessively near the end of last season, so I re-packed before splashing her in the spring.
Btw: I wouldn't go to the expense of one of those dripless systems. Gore GFO or GTU packing is said to be "virtually dripless," once properly installed, and is said to last a long, long time. Far cheaper and far simpler. I'm a strong believer in both
.
Jim