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INSTALLATION MANUAL

Install, plumb, break in and troubleshoot a PSS Type A or PRO dripless shaft seal for shafts ¾" to 3¾" (20 to 95 mm), with the bellow compression chart and the inspection intervals.

DocumentPSS Type A & PRO Shaft Seal Installation Instructions
FormatPDF · 8 pages · 1.0 MB
LanguageEnglish
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ComponentsBefore You StartInstallationCompressionPlumbingTesting & TroubleshootingInspectionProducts
PSS Type A & PRO Shaft Seal — Installation Instructions

What Is in the Box

Component Qty / note
Stainless steel hose clamps 4
Nitrile bellow 1 (PRO Seal uses a silicone bellow)
Carbon graphite flange 1
Stainless steel rotor 1
Stainless steel set screws 5 (4 for the rotor, 1 spare)
Nitrile O-rings 4 (2 in the rotor, 2 spare)
Stainless steel hose barb fitting With hose barb insert and washers
Clamp jackets 4 (hose clamp tail covers)
Retention collar 1 (PRO Seals only)

Before You Start

  • Install only with the boat out of the water, by a qualified installer.
  • No oil, grease (petroleum) or silicone anywhere in the job. Lubricate the rotor O-rings with soap and water.
  • Keep the carbon face and the rotor face clean and unscratched.
  • If the transmission comes out, or the boat is launched without it, hold the shaft so the bellow stays in its compressed position.
  • Never re-use the cupped-point set screws; replace any that have flattened.
  • Do not use sealant on the bellow-to-stern-tube joint or the hose barb.
  • Do not use an ozone generator aboard; ozone and sulfuric acid vapour from non-sealed batteries speed up rubber deterioration.
  • Never run the seal dry.

Installation Steps

  • 1–3. Unbolt and remove the shaft coupling; remove the old stuffing box and packing (classic, bolt-on or threaded glands).
  • 4. Dress the exposed shaft with #400 or #600 grit paper. Remove every sharp edge, especially the keyway the rotor passes over.
  • 5. Slide bellow and clamps onto the bare stern tube. The bellow should overlap the tube by the cuff length only; too far and the tube edge damages the inner ribs. Clamp it and fit the clamp tail covers.
  • 6. Check the carbon flange is clamped on the forward end of the bellow and its face is flawless.
  • 7. Check both O-rings are in the rotor bore. Thread in two set screws with a drop of blue thread-lock, short of the bore.
  • 8. Lubricate with soapy water and slide the rotor onto the shaft.
  • 9–10. Refit the coupling to the shaft and to the transmission to the manufacturer's specs, with all safety devices.
  • 11. Centre the carbon on the shaft at rest (its bore is larger than the shaft – normal), check the cuff and the shaft position in the log, and tighten all clamps.
  • 12. Slide the rotor until it just touches the carbon and mark this "neutral" position on the shaft.
  • 13. Push the rotor aft to compress the bellow by the chart amount and tighten the two set screws.
  • 13.1. PRO only: fit the two-part collar against the rotor and tighten its screws.
  • 14. Add the two locking set screws, with thread-lock, on top of the first two.

Bellow Compression & Torque

Shaft diameter Type A compression PRO compression
¾" to 1⅛" (20 to 29 mm) ¾" (20 mm) ¾" (20 mm)
1¼" to 1⅜" (32 to 35 mm) ¾" (20 mm) ¾" (20 mm)
1½" to 2½" (38 to 64 mm) 1" (25 mm) ¾" (20 mm)
2¾" to 3¾" (70 to 95 mm) 1" (25 mm) 1" (25 mm)

Set screw torque: approximately 6 ft-lb for shafts ¾" to 1⅜" and 8 ft-lb for 1½" to 3¾". The chart values are averages; engine mounts and water pressure change the exact amount needed.

Under 12 Knots

  • Sailboats and displacement boats under 12 knots under power, with no bearing in the shaft log, can use a vent line or a water feed.
  • Vent: ⅜" (8 or 9 mm) ID underwater-rated hose (not supplied) on the barb, double-clamped, run to at least 2 feet above the waterline near the centreline.
  • Secure it so it can never drop below the waterline. No loop at the top (siphon risk), and never plug the end.
  • Displacement boats with a bearing in the shaft log, and any boat whose stern tube can come out of the water, must plumb a water feed.

Over 12 Knots

  • A water supply is required: at speed a vacuum in the stern tube pulls water away and the carbon can overheat.
  • Maximum water pressure 10 PSI.
  • Sources: a T off the raw-water cooling line (T-kits for ¾", 1", 1¼", 1½" hose), the heat exchanger or raw-water-cooled manifold drain, or a scoop with a flow-regulating valve.
  • Twin engines that can exceed 12 knots on one engine need a crossover line between the seals.
  • Follow proper boat plumbing practice, e.g. an anti-siphon fitting if the pick-up is below the waterline.

Testing, Break-In & Troubleshooting

  • At launch the seal must not leak at rest. Run in gear: a fine mist and some carbon dust are normal while it beds in.
  • Break-in: about one hour of running while the carbon polishes the rotor face.
Symptom Fix
High-pitched squeal The seal is not getting water: correct the plumbing. Careful – faces may be very hot.
Spray or mist after break-in Check the compression; add a further ¼" and repeat until the spray stops.
Dripping at rest Debris between rotor and carbon: work a clean rag around between the faces so incoming water flushes it out.

Inspection & Replacement

  • Inspect the bellows at least every 6 months for cracks, splits, tears or brittleness; replace at the first sign.
  • Replace the bellow regardless of condition at least every 6 years (Type A) or every 8 to 10 years (PRO).
  • Replace any hose clamp showing corrosion. There are four.
  • Laid up for 3 months or more: pull the carbon face back to let a little water in.
  • Keep fuel, oil and corrosive liquids off the seal, e.g. when winterising the engine.
  • The shaft should run near centred and parallel to the shaft log.

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