PSS Shaft Seal
PSS Shaft Seal 02-212-400 2-1/2" Shaft 4" Stern Tube Marine Mechanical Seal
PSS Shaft Seal 02-200-314 Marine Mechanical Shaft Seal 2" Shaft 3-1/4" Tube
About PSS Shaft Seal
When it comes to keeping water where it belongs — outside your hull — few innovations have made a bigger impact on recreational and commercial boating than the PSS Shaft Seal. Manufactured by PYI Inc. and introduced in 1991, the PSS (Packless Sealing System) quickly became the world's best-selling marine mechanical shaft seal, and it has held that distinction ever since. From weekend cruisers to ocean-crossing superyachts, the PSS Shaft Seal is trusted across virtually every class of vessel imaginable.
How It Works
Traditional stuffing boxes and packing glands require constant adjustment and are designed to drip — a messy, time-consuming compromise that boaters have tolerated for generations. The PSS Shaft Seal takes a fundamentally different approach. PSS shaft seals and accessories use a mechanical face seal design in which a rotating stainless steel rotor presses against a stationary carbon-graphite flange. A flexible bellows connects the carbon flange to the vessel's stern tube, and water pressure maintains constant, even contact between the two sealing faces. The result is a completely dripless, 100% watertight seal that is also self-aligning — able to compensate for shaft misalignment and drivetrain vibration without any input from the owner.
A Seal for Every Vessel
PSS offers several seal configurations to match the full range of marine applications. The flagship Type A Seal covers propeller shafts from 3/4" to 3-3/4" in diameter — the most common range for pleasure powerboats and sailboats. The heavy-duty Type B Seal handles large commercial and military shafts from 4" to 6" in diameter, while the PSS PRO Seal adds a reinforced silicone bellows, a secondary shaft retention collar, and premium 316 stainless steel hardware for demanding, high-pressure, or corrosive environments. A dedicated Rudder Seal rounds out the lineup for vessels needing a reliable seal at the rudder stock as well.
Maintenance-Free Reliability, Certified by Leading Authorities
One of the most compelling reasons boat builders and owners alike choose PSS is the near-zero maintenance requirement. Unlike traditional packing glands that need periodic tightening and repacking to prevent excessive leaking, the PSS Shaft Seal is virtually maintenance-free once installed. Boatyards appreciate that it eliminates bilge water accumulation and reduces wear on expensive propeller shafts. The PSS Shaft Seal is certified by Bureau Veritas, ABS, and RINA, and has been installed as standard equipment by prestigious builders including Nautor Swan, Little Harbor, and Boston Whaler. It is also widely recognized as the premier retrofit solution for existing vessels, fitting shafts ranging from 3/4" to 6-1/2" across both metric and imperial dimensions.
A Complete Ecosystem of Accessories
Beyond the core seal assemblies, PSS offers a full range of supporting hardware and maintenance items through their packing boxes, shaft seals & accessories lineup. Shaft retention collars, seal retention collars, O-ring kits, silicone hose, T-kits, maintenance/service kits, and the innovative FlowTrue cooling water management system all work together to ensure long service life and trouble-free operation. Whether you are doing a new installation or refreshing an existing seal, PSS has the components to do the job right.