How do I replace the stern gland (shaft seal) on a Hallberg-Rassy 31?

First check whether your Hallberg-Rassy 31 has a conventional propeller shaft: HR 31 Mk I and Mk II boats commonly have a Volvo Penta saildrive, which uses a hull diaphragm rather than a stern gland. If yours has shaft drive, replace the gland ashore by disconnecting the shaft coupling, removing the old seal and fitting the correctly sized replacement with its installation sleeve.

Identify the drive and seal

Look behind the engine. A conventional installation has a shaft running aft through a seal attached to the stern tube; a saildrive has a transmission leg passing down through a large rubber diaphragm in the hull.

If you have a saildrive, stop here. Replacing its hull diaphragm involves supporting and separating the drive, and usually moving the engine. Water in the saildrive oil calls for a different investigation, including the propeller-shaft seals in the lower unit. Neither job follows the stern-gland procedure below.

For shaft drive, identify the seal fitted. Previous owners may have changed it:

• Volvo Penta rubber lip seal: a compact black rubber body clamped onto the stern tube.
• PSS face seal: rubber bellows, a stationary carbon face and a stainless-steel rotor secured to the shaft.
• Packed stuffing box: a metal gland with an adjustable packing nut or follower.

Measure the shaft diameter and stern-tube outside diameter with callipers, and photograph the coupling and seal markings. Do not order by boat model alone. Hallberg-Rassy manual passages labelled for centre-cockpit boats do not specify the installation on the aft-cockpit HR 31.

Disconnect the shaft

Have the boat securely supported ashore. Isolate the engine starting circuit and prevent anyone turning the shaft while your hands are around the coupling.

For a rubber lip-seal replacement, gather the correct seal kit, supplied installation sleeve, specified lubricant, replacement clamps where required, sockets, a torque wrench and a suitable coupling puller.

1. Clean the area and mark the shaft position at the coupling, including its insertion depth.
2. Support the shaft before disconnecting the coupling from the gearbox flange.
3. Release the shaft from its coupling using the coupling manufacturer's procedure. Split-clamp, taper and solid couplings require different methods.
4. Move the shaft aft only as far as necessary, with someone outside watching propeller-to-rudder clearance.

Check that there is enough clearance before dismantling. Removing the coupling from the shaft may give you the access needed; other arrangements require propeller removal or further shaft withdrawal. Never hammer the shaft against the gearbox or use the rudder as a stop.