As you can gather from the posts above, this is a topic where there’s a wide range of opinions and preferences.
One of my mottos is that when intelligent people disagree, there’s a good chance that all are right – just in different circumstances.
That said, I’ve had PYI’s PSS dripless on multiple boats, never had a problem. The water lubrication that Mark recommends is extra protection and does eliminate the initial burping when going back in the water. And, the cap they tell you to buy if you don’t install it is surprisingly expensive. However, the last time I looked at the PYI documentation, they said water lubrication was really only mandatory for boats that exceed 10 kts under power (i.e., in your dreams for our Nonsuches).
Joe has a point that failure would be bad. The situation in which that could occur is if the collar on the shaft (which PYI refers to as the, “rotor”) were to somehow slide up, stop compressing the bellows attached to the stern tube, and thereby lose contact with the “stator” (the matching frictionless plate). Water would then comes through the resulting gap, just as it would if your stuffing box was to come unscrewed and unstuffed.
However, just as stuffing box flanges can be prevented from unscrewing by proper installation, you can avoid the small risk of the shaft attachment sliding up from proper installation. Their shaft collar goes in with two cupped set screws, one on top of the other. The first one holds the collar to the shaft, the second one keeps it there. Don’t reuse those screws, they depend on having a shape that binds them well to the shaft the first time, but doing so changes the shape so they’re not good a second time.
For not very much money, you can also get an extra shaft collar either from PYI or from a reputable outfit like McMaster-Carr. If you want extra insurance, install that immediately forward of the PYI PSS shaft collar. Then your pants have both a belt and suspenders and you won’t get caught with them down.
Joe is also raising an important consideration in mentioning that major repair/replacement has to be done out of the water. In addition, although he didn’t mention it, the set screws are the only component you can replace with disconnecting the shaft. All the other components slide into place around the shaft and shaft log. Depending on how hard your shaft is to disconnect and how hard it is to do a realignment afterwards, that can turn into a real cost. On the other hand, this is something you’d need to do around every 6-8 years or so. I, for one, haul my boat considerably more often that that anyway. So that aspect of the stuffing box vs. dripless choice comes down to whether you want to spend some time and money every season vs. spending somewhat more time and money but having to do so less often.
There really isn’t a wrong choice, just tradeoffs IMHO.
– Bob
Me Gusta
Nonsuch e26U #233
Looking forward to seeing folks in Toronto:
https://nonsuch.org/2024-INA-International-Rendezvous-Status
