How do I replace the stern gland (shaft seal) on a Hallberg-Rassy 39?

Replace the shaft seal on your Hallberg-Rassy 39 ashore by disconnecting the propeller shaft from its coupling, making room to slide off the old gland and fitting the correctly sized replacement. Identify the fitted seal and coupling first, because equipment changes over the boat's life make the model alone an unreliable parts specification.

Identify the fitted gland

Clean the gland and photograph its markings, stern-tube connection and gearbox coupling. A Volvo Penta rubber lip seal, a traditional packed gland and a PSS mechanical face seal need different parts and commissioning procedures.

• Rubber lip seal: usually a moulded black rubber body clamped to the stern tube, with sealing lips running directly on the shaft.
• Packed gland: a metal housing with an adjustable packing nut or follower.
• Mechanical face seal: a rubber bellows, stationary sealing face and stainless rotor secured to the shaft.

Measure the shaft diameter with a vernier calliper on clean, unworn metal. Then measure the stern-tube outside diameter where the gland attaches. Both dimensions matter. Do not substitute a near-matching imperial size for a metric shaft. Record any vent or cooling-water connection and check the replacement manufacturer's requirements.

Allow roughly £150 to £300 for a conventional rubber seal kit. Mechanical face-seal kits generally cost more. These figures are budgeting allowances and exclude lifting and labour. A seized coupling can take more work than the seal replacement itself.

Disconnect and check shaft clearance

Have the boat securely supported ashore and isolate the engine starting circuit before opening the stern tube or working on the shaft.

1. Expose the coupling and gland, clear the working area and photograph the assembly before dismantling.
2. Mark the coupling halves' relative positions and record the shaft's fore-and-aft position. Support the shaft so its weight cannot hang on the gland.
3. Disconnect the gearbox coupling, including any flexible coupling fitted. Identify how the shaft is retained: split clamp, taper and nut, key, grub screws or another arrangement.
4. Release the shaft coupling with the correct puller or extraction arrangement. Do not hammer the shaft or use the gearbox flange as an improvised press.
5. Check that the shaft can move aft far enough to expose its forward end and let the gland slide off.

On an HR 39, shaft movement depends on the fitted coupling, propeller and clearance ahead of the rudder. Check these physically before pushing the shaft aft. If there is too little clearance, you may need to remove the propeller, withdraw the shaft further or move the engine. Bring in a marine engineer at that point.