Tired of leaky shaft seals filling the bilge with water or having to replace the packing? The solution is to replace the old stuffing box with a new dripless shaft seal. I’ve written about repacking a traditional stuffing box in the past, so now I’ll walk you through upgrading to a dripless shaft seal.
With the boat out of the water, you can disconnect the shaft coupling from the transmission and slide the shaft out enough to remove the old stuffing box, inspect the shaft for excessive wear or electrolysis in that area, and install a new dripless shaft seal. Last spring, that is just what my buddy Jeff did on his 30-foot sailboat. He happened to remove the transmission from his Yanmar 2GM diesel for repair, so while he had the assembly apart he took the opportunity to also install new engine mounts, check the alignment, and install a new PSS (Packless Sealing System) from PYI.
Before I go on, I’d like to explain two things. First, there are different types of dripless shaft seals — lip seals and face seals. The PSS one I’m recommending is considered a face seal, which mechanically mates two smooth surfaces together by compression. My second point is that I don’t want you to think that by installing a dripless shaft seal it means that it is completely maintenance-free. It’s a boat, so nothing is maintenance free, but these seals do require less maintenance than stuffing boxes, and they reduce shaft wear. Finally, as the name suggests, they don’t drip — at least when they’re properly installed and maintained. The resultant dry bilge is worth the investment, in my opinion. I’ll give you a handy link at the end of this blog if you want to see what kind of maintenance issues might arise.
Back to the installation. The most important aspect is to make sure the shaft is clean and smooth, so that the new mechanical seal mates properly and that you won’t damage the seal as you’re fitting it onto the shaft. So, once you’ve disconnected and removed the shaft coupling from the transmission, clean the shaft with a piece of emery cloth or fine sandpaper. Inspect it for any electrolysis damage or scoring where the old stuffing box was. If the shaft is pitted excessively there beyond your ability to sand and smooth it, you may want to consider replacing the shaft, as it will never mate effectively enough to provide the desired seal.
After the shaft is clean and smooth, slide the PSS bellows over the shaft until it is seated against the boat’s shaft log. Next, using a little soapy water, slide the stainless collar that contains the two rubber O-rings onto the shaft. Reconnect the shaft coupling to the transmission. Attach the hose clamps to the shaft log, then tension the bellows per the installation instructions and tighten the set screws on the stainless steel color. It’s fairly straightforward — here’s a YouTube video from Go2Marine.com showing how simple the PSS Installation is:
One additional comment I have beyond the video is that I like to put a sacrificial shaft zinc directly in front of the stainless steel PSS coupling. This protects the shaft against electrolysis and acts as a safety in case the set screws fail. Finally, follow the instructions for proper placement of the vent tube.
A dripless shaft seal will cost between $200 and $1,200, depending on how big your boat is (shaft size and shaft log size), but in general closer to the $200 figure. This is a small price to pay to avoid the drip, drip, drip of an old-fashioned stuffing box and the resultant mold and mildew problems often associated with a wet bilge.
As I said before, nothing on a boat is maintenance-free. For more information on potential problems and troubleshotting tips on dripless shaft seals, click here. Good luck!