I am installing a Volvo drip less shaft seal in the repower of our E34. Much simpler mechanically and been in use since the 1990’s. No experience with it yet. The boatyard recommended it as a way to save some space between the stern tube and the shaft coupling.
The shaft tube OD is about 1-1/2” (the tape measure is not perfectly aligned in the photo).
His conclusion is that you need to pay attention to your dripless shaft seal, that's all.
However, from my perspective as a trawler owner and towboat operator, a brand new dripless shaft seal, properly installed, will do exactly what the manufacturer claims it will do: provide a vibration-tolerant, drip-free stuffing box. Be sure to read and follow the manufacturer's installation and maintenance instructions, and keep the literature close at hand so that it will remain in your mind as you perform routine maintenance in your trawler's engine room.
I have the PYY dripless shaft seal in my boat, came with the boat. Was unable to determine it's age when i purchased the boat a year ago. The surveyor noted the rubber bellows appeared to be at or beyond the 10 year replacement interval based on condition.
There are few things more inconvenient than having a shaft seal fail, and I prefer not to worry about such things. At my first haulout I had it addressed along with a new cutlass bearing since they had to pull the shaft anyway. I learned there is actually an overhaul kit for the PYY that was about $300 installed --cheap insurance I thought. Whole unit looks like new again. Overhaul was much cheaper than installing a new unit.
Last anecdotal story that might be worth consideration... my slip neighbor recently had the misfortune of having a terry cloth towel fall through the bottom of his cockpit locker and get wrapped up in his PYY shaft seal... which commenced to leak a considerable amount of water. Clearly there were fibers caught between the two mating surfaces. I tried to help him extract them, but we were not successful -- I assumed he would need to haul the boat to fix it. To my surprise, a mechanic came over from the yard... loosened the stainless collar with an allen wrench... a slipped out the offending detritus... no haul out required. Made me think it was good to have a very common unit, which I think the PYY is.
@racushman Regarding your last anecdotal story, PSS specifically states that you should never reuse the set screws in the collar. You must always replace them with new. The article I mentioned above repeats this warning about not reusing set screws