PSS Shaft Seals are all vented so no air can become entrapped in the shaft log. An air-bound shaft log can result in the PSS running dry and becoming extremely hot. If the shaft log becomes air entrapped the rotor faces lack lubrication, and the PSS is a water lubricated shaft seal.


Despite many rumors and mistruths about slow turning shafts not needing to be plumbed or vented the reality is that even slow turning shaft vessels can develop entrapped air up in the shaft log.


The vented or plumbed hose keeps the seal faces lubricated by injecting, venting or displacing the air and allowing water to take its place. The problem is this hose needs to be routed above the waterline with no low spots if used for venting. Low spots trap water, like the p-trap under your sink, and thus preventing the venting of entrapped air.


In this Catalina 310 it was difficult to find a route that would not result in a low spot where water could become trapped. The engine compartment route was the only way I found that did not hold water or impeded the flexibility of the vent hose on the shaft seal.


Routing into the engine compartment, on this particular boat, solved this problem and the water bottle kept burped salt water off the engine. The hose barb pictured just pressure fits nicely and is easily removed to empty the bottle from reverse thrust burping.