PSS Seal Failure

leo310

.
Dec 15, 2006
635
Catalina 310 44 Campbell River BC
I had a PSS Seal replaced last year with the same type that serviced the boat for 18 years. This unit as per manufacture spec did not need water seal line from the raw water pump. What we found is on the Catalina 310 the shaft is right at the water line and the top of the seal may or may not get any water and will over heat and fail. What is now recommended is no matter what add a water line to the seal from the raw water pump. I was lucky as this was covered by the warranty parts and labor,
 

Ted

.
Jan 26, 2005
1,254
C&C 110 Bay Shore, Long Island, NY
The prop shaft looks to be well below the waterline in this drawing from the Sailboatdata site. Maybe the bellows weren't burped properly.

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Jul 7, 2004
8,402
Hunter 30T Cheney, KS
I don't see the issue either. I wouldn't disagree though if they say the warranty covers it. What failed exactly? You did have a hose on the barb to vent it right?
 

leo310

.
Dec 15, 2006
635
Catalina 310 44 Campbell River BC
Ran all summer with no problems and after oil change thats when it failed, the boat is out of the water once a year and that was Apr 2020.
Yes the new PSS has a barb that's connected to the raw water the other 2 did not. It was the carbon face that failed, the leak was about 5 gal/24hr.
As for the water line it's just below the top of the seal on our boat, we checked it out using the water discharge thru-hole.
 
Jul 7, 2004
8,402
Hunter 30T Cheney, KS
When you say "other 2 did not", does that mean they didn't have a vent hose at all or not connected to a positive water source?
If the waterline is that low, I wonder why the seal hadn't failed earlier than 18 years. Do you need more weight aft?
 
Oct 26, 2010
1,881
Hunter 40.5 Beaufort, SC
Something is really wrong here. Most sailboats (if not all) are designed such that the shaft enters the hulls below the waterline. I doubt seriously that Hunter built the OP's boat with a PSS seal installed, just from the price point standpoint. With a suffing box and packing it MUST have water cooling when operating to keep it cooled, thus the small drip desired when adjusting the packing. With no cooling water, the packing will burn up very quickly. Replacing with the stuffing box with a properly installed and maintained dripless shaft seal should not change anything in the geometry. If it burned up then something is wrong with the installation OR the boat is not sitting on its lines to a pretty serious degree. To lift the shaft entry point so high that water would not be available to cool the PSS or stuffing box would be pretty obvious when looking at the boat sitting in the water! I suspect as others have suggested that the PSS seal had an air lock somehow keeping cooling water from reaching the seal.
 
May 17, 2004
5,025
Beneteau Oceanis 37 Havre de Grace
Something is really wrong here. Most sailboats (if not all) are designed such that the shaft enters the hulls below the waterline. I doubt seriously that Hunter built the OP's boat with a PSS seal installed, just from the price point standpoint. With a suffing box and packing it MUST have water cooling when operating to keep it cooled, thus the small drip desired when adjusting the packing. With no cooling water, the packing will burn up very quickly. Replacing with the stuffing box with a properly installed and maintained dripless shaft seal should not change anything in the geometry. If it burned up then something is wrong with the installation OR the boat is not sitting on its lines to a pretty serious degree. To lift the shaft entry point so high that water would not be available to cool the PSS or stuffing box would be pretty obvious when looking at the boat sitting in the water! I suspect as others have suggested that the PSS seal had an air lock somehow keeping cooling water from reaching the seal.
Between the length of the bellows and diameter of the faces I guess it’s possible that the contact surface of the PSS be higher than the original stuffing box. Maybe that extra height is just enough to get above the waterline.
 
Oct 26, 2010
1,881
Hunter 40.5 Beaufort, SC
Between the length of the bellows and diameter of the faces I guess it’s possible that the contact surface of the PSS be higher than the original stuffing box. Maybe that extra height is just enough to get above the waterline.
Good point @Davidasailor26 - geometry would be changed by the sine of the angle of entry times the length of the PSS to the face of the carbon ring. @leo310 - What is the "water thru-hole discharge" A better way to tell should be easy enough. Just grab the carbon ring and pull aft on it (to compress the bellows a little) and if water comes in, its below the waterline. If water does not, its above the water line OR something is blocking the shaft tube from outside the hull. Was the oil changed when the boat was out of the water? I wonder if its possible that some yard worker stuffed something around the shaft when it was on the hard or if some growth has plugged the area around the shaft so that water cannot freely flow into the bellows from outside the hull?

Although I'm not familiar with the OP's specific boat, its still hard to understand how the shaft entry point is only 3 or 4 inches or so below the waterline. I have three thuhulls (Engine, Generator, and Air Conditioner) all in the area well aft of the shaft tube/PSS seal and therefore at or above the carbon ring. I'd be sucking air from all three if the geometry were the same on my boat. Also add to this that almost all Hunters that I know of squat a little when under power, increasing the margin from the PSS to the water line. That is why I said something is really wrong here.

A key to the problem not being geometry is in the OP's original post which said " Ran all summer with no problems and after oil change thats when it failed" Nothing in changing the oil should have changed anything with the PSS so something else changed.
 
Feb 14, 2014
7,399
Hunter 430 Waveland, MS
New PSS seal can be over compressed.

The Carbon composite face will wear evenly, unless there is misalignment on the shaft.

Even at lower propeller RPM, that seal will wear, if no water lubricant is provide.

One other thought,
If his shaft tube has a way to trap air, in that cavity along the hull line, he will never get back flow water to lube the seal.
Jim...
 
Feb 14, 2014
7,399
Hunter 430 Waveland, MS
the leak was about 5 gal/24hr.
This is the biggest clue.

He has to have water touching the PSS seal face.

Thus, my best guess...
Over compression of seal, with a touch of misalignment.
Jim...
 
Oct 26, 2010
1,881
Hunter 40.5 Beaufort, SC
+1
Wonder if the person changing the oil stepped on the bellows or carbon ring putting it out of line and then wearing the carbon ring face unevenly. I know if I grab the carbon ring and shift it left or right even a little water comes out until I readjust it evenly so the carbon ring is faced squarely on the rotating ring.. If it gets stepped on, putting it out of alignment I can see it leading to this problem.
 
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