PSS Type B Shaft Seal, 4" Tube, 6-1/2" to 6-5/8" Stern Tube

These heavy duty Type B shaft seals are designed for propeller shafts from 4" to 6" in diameter.

A shaft seal prevents lake or seawater from entering your boat through the stern tube opening where the propeller shaft exits the vessel.

An attractive alternative to traditional high maintenance and constantly dripping flax packing boxes, the Type B Packless Shaft Seal is a watertight mechanical face seal. The sealing surface is created between the flat surfaces of a spinning stainless steel rotor (attached to the prop shaft) and a stationary carbon-graphite stator collar (attached to the boat's stern tube via a flexible hose bellow).

The stainless steel rotor is located on the shaft just inboard of the carbon stator. The rotor is then pressed against the stator to compress the spring-like bellow before the rotor is secured to the shaft with set-screws. This compression (pre-load) maintains a constant firm contact between the two flat faces of the rotor and the carbon stator, allowing the PSS to compensate for the variable fore and aft movement due to propeller thrust.
The carbon stator is over-bored to the shaft diameter allowing it to “float” around the shaft and thus compensate for most misalignment and engine vibration problems.
The stainless steel rotor is sealed to the shaft by two O-rings that are recessed into the bore of the collar. These O-rings rotate with the shaft and stainless-steel rotor and do not experience wear during operation.

All shaft seals include a hose barb fitting on the carbon flange for either simple venting to air above the waterline (to let any trapped air escape the seal on low speed boats), or for a cooling water feed (on vessels over 12 knots) which is easily installed with the use of a Water Pick-Up Hose Tee Kit, sold separately. High speeds can create a vacuum in the seal, starving it of lubricating water.
On twin engine installations, the cooling water plumbing must be linked between engines in case one engine is shut down while the other continues to power the boat in excess of 12 knots - this ensures both seals remain lubricated. See Installation Instructions.

These dripless shaft seals finally allow you to experience dry bilges – no more wetness, packing replacement, shaft wear or needless periodic bilge pumping!

PSS Features –
• Self-aligning high density carbon-graphite stator ensures a 100% watertight seal with proven reliability
• Tough, chemical and fuel resistant nitrile rubber bellow presses the rotor against the stator to make a watertight seal
• Eliminates shaft wear and minimizes corrosion
• Requires virtually no maintenance and is provided as standard equipment by many of the world's finest builders and the U.S. Coast Guard
• Can be installed as a replacement for a leaking packing gland or on shafts in less than ideal condition – say from packing wear
• Precision seal - no spray guard, no dripping
• Unaffected by engine motion or vibration
• Highest quality materials and computer-precision machining
• Type B Rotors are manufactured out of Nitronic 50 - a very high grade stainless steel alloy which is almost totally corrosion resistant
• 3-year limited warranty

PSS shaft seal standards –
• Temperature Limits: -13°F to 425°F (-25°C to 220°C)
• Pressure Limits: 50 PSI (3.5 BAR)
• Shaft RPM Limits: 7,000 RPM
• Carbon/Graphite Stator: Lapped to 4 HLB (0.000044" tolerance)
• 316 (std)/Nitronic 50 (opt) stainless steel Rotor: Faced to 9 Ra
• Bellow Material: mandrel formed silicone and fabric