PSS type A propeller shaft seal – 38mm propeller shaft x 69.9mm housing

Description

PSS Type A Propeller Shaft Seal (Shaft Seal)

The PSS Type A propeller shaft seal is a high-quality mechanical shaft seal for recreational and commercial shipping. This low-maintenance sealing system replaces the traditional stuffing box and ensures a completely dry bilge. Thanks to the combination of a stainless steel rotor and a carbon stator, it creates an extremely reliable, wear-resistant, and leak-proof seal.

This seal is designed for long-term performance, even under heavy conditions, and is used worldwide in both recreational and commercial vessels.

Technical specifications

• Temperature range: -15°C to +107°C
• Maximum working pressure: 0.68 bar
• Maximum shaft speed: 10,000 RPM
• Carbon graphite sealing face: Lapped to 4 HLB (0.000044″ tolerance)
• Rotor finish: ≤ 13 Ra
• Rotor material: 316L stainless steel (optional Nitronic 50)
• Bellow material: Cast Nitrile (NBR) – PVC

Installation manual: Manual PDF

How the PSS Type A Seal works

The seal consists of a rotating stainless steel rotor pressed against a stationary carbon stator. These precisely finished contact surfaces create a watertight mechanical seal. During the initial running hours, the stainless steel rotor polishes the carbon sealing face for optimal fit and maximum lifespan.

Stainless Steel Rotor of the PSS Type A

The rotor is made of 316L stainless steel and CNC-precision turned with a surface finish of ≤ 13 Ra. It is attached to the shaft using two sets of adjustment screws at 90° for maximum retention and grip.

High-Density Carbon Stator

The stator is made of a high-density, resin-impregnated carbon composite. The material is formed under pressure, baked, machined, and then lapped to a flatness of 4 helium light bands (0.000044″ tolerance).

Benefits of this carbon composite:

• Resistant to temperatures up to 260°C
• Does not melt during brief dry running
• Extremely high wear resistance
• Long lifespan (more than 40,000 engine hours recorded in commercial applications)

Bellow

The bellow is cast from a high-quality Nitrile (NBR) compound with excellent resistance to petroleum products. The material combines durability, elasticity, and strength — essential for reliable axial compression of the seal.

Cooling and Ventilation

For fast vessels (from approx. 12 knots), a positive water supply is required for lubrication and cooling of the sealing surfaces. For slower boats (under 12 knots) without a bearing in the propeller shaft tube, ventilation is usually sufficient. The ventilation hose should ideally be mounted 60–90 cm above the waterline and as close as possible to the centerline to prevent water ingress during tilting.

FAQ – Frequently Asked Questions

When should I replace the PSS rubber bellow?
The bellow of the PSS Type A propeller shaft seal should be replaced as preventive maintenance at least every 6 years. This applies to the Type A Seal.