PYI - PSS Shaft Seal Maintenance Kit

The PSS PRO bellow, like any rubber or silicone hose used below the waterline, should be regularly inspected for wear, aging, or chemical deterioration, with PYI recommending preventive replacement every 8-10 years. During this replacement, it is advisable to also replace the o-rings and set screws in the stainless steel rotor. Set screws should never be reused; each rotor hole contains two set screws—one securing the shaft and the other locking it in place. These screws have a cup base that grips the shaft, and PYI's PSS Maintenance Kit includes five new screws for reinstallation. If spares aren't available, the existing screws should be reversed to use the unused cup for a secure fit.

KIT CONTENTS

• Silicone Bellow - 1qty
• Bellow rings – 3qty (Standard on sizes 2-1/4" (60mm) to 3-3/4" (95mm) and optional for smaller sizes)
• Nitrile o-rings - 2qty
• 316SS Hose clamps - 4qty
• Tube of Thread Lock - 1qty
• Allen key - 1qty

DIMENSIONS

Shaft Diameter: 7/8"
Stern Tube Diameter: 1-1/4" to 1-3/8"

How Does It Work?

1. Two nitrile o-rings seal the stainless steel rotor to the shaft and will not experience wear.

2. The Shaft Retention Collar is attached to the shaft and helps retain the propeller or rudder shaft in your vessel in the event of catastrophic failure of the coupling or if the shaft comes free from the coupling.

3. A seal is created between the two mating faces of the carbon stator and the stainless steel rotor.

4. A seal is created between the two mating faces of the carbon stator and the stainless steel rotor.

5. Raw water is fed to the PSS Shaft Seal for cooling / lubricating the seal faces on high speed vessels.

6. Hose clamp tail protection, Clamp Jackets.

7. The stationary carbon stator is attached to the bellows, which is secured to the stern tube (shaft log).

8. 316SS hose clamps with rolled edges and non-perforated band

Shaft Retention Collar

The PYI Shaft Retention Collar is designed to help retain the propeller or rudder shaft in your vessel in the event of catastrophic failure of the coupling or if the shaft comes free from the coupling. The double split design provides the maximum in axial holding power with the benefit of quick and efficient assembly with the shaft installed. Design fully engages the shaft without marring. Easily installed where major disassembly would otherwise be required. Greater axial holding power than set screw or one-piece clamping collars. Effective on hard and soft shafts.

Rotor

The PSS stainless steel rotor is slid down the shaft and is secured to the shaft with set screws at 90° for maximum holding power. Precision tolerances are maintained by computer controlled lathes. The faces have a number 9 micro finish and are perpendicular to the bore to prevent run-out as the collar rotates. The carbon graphite stator will polish the face of the rotor during the first few minutes of operation. The stainless steel rotor should not need to be replaced under normal operating conditions. The stainless steel rotor used on the PSS Type A Shaft Seal is made from 316L stainless steel.

Carbon Stator

The high density, resin impregnated carbon/graphite stator is a composite that is first mixed, molded and then formed under pressure. The blanks are then baked, machined and lapped. The face of our carbon is finished to a flatness of 4 helium light bands (measured .000044" of variation over entire lapped surface). The grade of carbon used in the PSS has an operating temperature over 500° Fahrenheit (+260° Celsius), and cannot melt if the seal runs dry, unlike a rubber lip seal or plastic face seal. The high density of the carbon greatly increases the longevity and wear resistance. Several commercial vessels have recorded over 40,000 (over 4-1/2 years of continuous operation) engine hours on the same, original components. The carbon should not need to be replaced under normal operating conditions.

Carbon Stator

The PSS PRO Shaft Seal bellow provides the best combination of durability, strength and elasticity. It's constructed of four ply aramid / silicone with a flurosilicone outer. This flurosilicone cover creates an oil and fuel resistant barrier protecting the exterior surface from the possibility of damage from splash or spill. Both ends of the bellow are sealed. The four ply cloth inlay provides excellent strength and resistance to abrasion. This bellow has a continuous operating temperature range of -90°F to +425°F (-70°C to +220°C).

FAQs

What general maintenance should I be considering for a PSS Shaft Seal that is working perfectly well with no apparent issues?

Given the quality of the PSS Shaft Seal this is what we would expect where very little maintenance is generally necessary. Typically the carbon and stainless steel sealing components will not need replaced where we see many commercial vessels recording over 40,000 engine hours on original components. That said, we do recommend the rubber bellow component be replaced in 6 year intervals as precautionary maintenance kit for this replacement which includes the rubber bellow and all necessary hardware.

Can I re-use my set screws when making an adjustment or removing the PSS Shaft Seal?

No, please be sure to never use the same set screw on the shaft twice. There are two set screws in each of the two holes in the stainless steel rotor. One is tightened onto the shaft and the other is tightened onto the first to lock it in place against the shaft. The set screws are made with a cup at the base that compresses into the shaft ensuring a secure grip. PYI's PSS Maintenance Kit comes with five new set screws included. When re-installing the rotor please use new set screws. In the case that you do not have spare set screws, the set screws in the rotor need to be reversed so there is an unused cup being compressed onto the shaft. (See image below for more details)

Installation Video