How do I replace the stern gland (shaft seal) on a Hallberg-Rassy 37?
I want to replace the propeller shaft seal on my Hallberg-Rassy 37 during the next lift-out. How do I identify the right replacement, get the shaft clear of the gearbox coupling and make sure the new seal is ready before running the engine?
Answer
Replace the stern gland on your Hallberg-Rassy 37 with the boat ashore: disconnect the shaft coupling and free the shaft's forward end so the new seal can slide on. First identify the fitted seal and measure its connections, as previous owners may have changed the installation and the seal type dictates lubrication, venting and fitting procedure.
Identify the fitted seal
Open the access around the gearbox and photograph the seal, stern tube and coupling before dismantling anything. A Volvo Penta rubber lip seal resembles a compact black rubber sleeve; a PSS face seal has rubber bellows and a stainless-steel rotor clamped to the shaft. A conventional packed gland has an adjustable packing nut or follower.
Do not order parts solely against "HR 37". Record:
- The shaft diameter, measured with vernier callipers on clean, unworn metal.
- The outside diameter of the stern-tube connection beneath the seal.
- The seal's moulded markings or part number, available installation length, and any vent or water-supply hose.
- The coupling type and the space available to withdraw the shaft aft.
A 30 mm shaft needs a 30 mm seal, not a nominally similar imperial size. That is a sizing example, not confirmation of your boat's shaft diameter. Obtain the replacement's installation sheet before starting. For a rough UK parts budget, allow £100 to £200 for a rubber lip seal or £300 to £500 for a mechanical face-seal kit, depending on size and supplier.
Release the shaft coupling
Have the boat securely supported ashore, isolate the engine starting circuit and secure the shaft against sliding out before disconnecting it.
- Mark the coupling flanges' relative positions and record the shaft's installed position. Support the shaft so its weight does not hang on the seal.
- Disconnect the gearbox flange bolts and identify how the shaft coupling is retained: split clamp, taper, key, nut or another arrangement.
- Release the coupling using its specified procedure and a suitable puller where needed. Do not hammer the shaft or use the gearbox flange as an improvised press.
- Move the shaft aft only far enough to remove the coupling and slide the seal off its forward end. Check external clearance first: the propeller, rope cutter and rudder can restrict movement.
- Loosen the seal's stern-tube clamp and remove the old assembly. Disconnect and label any hoses.
A seized coupling can become the biggest part of the job. If proper extraction equipment will not release it, call a marine engineer before damaging the shaft, coupling or gearbox output bearing. Rudder removal is not an automatic requirement; check the available clearance first.