How do I replace the stern gland (shaft seal) on a Hallberg-Rassy 34?

First check whether your Hallberg-Rassy 34 has a conventional propeller shaft or a Volvo Penta saildrive: many HR 34s have a saildrive, with a hull diaphragm rather than a stern gland. If yours has a shaft, replacing the seal normally means hauling out, disconnecting the shaft coupling and sliding the old seal off the forward end of the shaft.

Identify the shaft seal or saildrive

Look behind the engine. A conventional installation has a horizontal stainless-steel shaft running aft through a seal on the stern tube; a saildrive has a gearbox leg passing down through a large rubber diaphragm in the hull.

The parts and labour differ completely between the two installations. The engine model alone will not identify yours, particularly if the boat has been repowered or modified.

• Volvo-type rubber shaft seal: a moulded black rubber body clamped to the stern tube, with sealing lips around the rotating shaft.
• Mechanical face seal: typically a rubber bellows, stationary sealing face and stainless-steel rotor secured to the shaft, as on a PSS installation.
• Packed gland: a metal housing with an adjustable packing nut or follower.
• Saildrive: identify the drive model from its plate and distinguish the main hull diaphragm from the smaller propeller-shaft oil seals in the underwater gearcase.

Photograph the assembly and record its markings. For a shaft seal, measure the shaft diameter and stern-tube mounting diameter with callipers. A nominal 25 mm shaft seal will not fit a 1-inch shaft correctly.

Haul out and check access

Have the boat hauled out and securely supported. Isolate engine starting before loosening anything that seals the hull opening.

Clean the area to distinguish leakage at the shaft lips from leakage at the stern-tube connection. Check the rubber for cracks, the clamps for corrosion and the shaft for scoring. Water tracking down from elsewhere can make a sound gland appear faulty.

Check how the coupling attaches to the shaft and whether there is enough clearance to slide the shaft aft. The propeller, rope cutter, bearing arrangement or rudder may restrict movement. Withdrawing the shaft completely can require further dismantling.

Have the correct replacement seal, supplied fitting sleeve, specified lubricant, suitable clamps and coupling instructions ready. Useful tools include callipers, feeler gauges, a torque wrench and the correct coupling puller. A seized coupling is often the biggest obstacle.

Remove coupling and replace seal

1. Mark the shaft's position in the coupling and photograph the locking arrangements. Support the shaft before separating the coupling from the gearbox flange.
2. Remove the coupling using its specified release method. Do not hammer the shaft or use the gearbox flange as a reaction surface for improvised extraction.
3. Release the old seal from the stern tube and slide it off. Check the exposed shaft, including the area where the new sealing lips or rotor will sit.
4. Remove burrs around the keyway and coupling end without reducing the shaft diameter. Have deep grooves, pitting or a worn sealing track assessed before fitting new rubber.
5. Clean the stern-tube spigot. Fit the new seal using its protective sleeve to prevent sharp edges cutting the lips. Apply only the lubricant specified by the seal manufacturer.
6. Secure the seal and rebuild the coupling, including its key, fasteners and locking devices. Use the specified clamp and coupling torques; there is no universal HR 34 torque value.