How do I replace the saildrive diaphragm on a Hallberg-Rassy 42?
I'm planning to replace the rubber seal between the saildrive and hull on my Hallberg-Rassy 42. Can I tackle it ashore myself, and what needs disconnecting before the drive will come away from the engine?
Answer
Replacing a saildrive diaphragm requires a haul-out, independent support for the engine and drive, separation of the components specified in the drive's workshop manual, and the correct diaphragm kit. First confirm that your HR 42 has a saildrive: many have shaft drive, whose stern gland or shaft seal needs a different procedure.
Identify the drive and seal
Look beneath the engine and read the transmission identification plate. A saildrive has a substantial leg passing through a broad rubber diaphragm in the hull. A shaft-drive gearbox connects to a propeller shaft running aft through a stern tube.
The boat's model name alone cannot identify the seal kit, particularly after an engine replacement. Record the engine model, drive model and serial number, and photograph the mounting arrangement. Volvo Penta 120S, 130S and 150S installations are not interchangeable.
Distinguish the main watertight diaphragm from the thin external rubber fairing around the leg. Replacing that outer flap does not renew the hull seal. Check the diaphragm's installation date against the replacement interval specified for your drive. Appearance alone cannot establish its remaining service life.
Support the engine and drive
This is a substantial DIY job requiring lifting equipment, a torque wrench and the workshop instructions for the exact model. On an HR 42, access and space to move the engine can determine whether a competent owner can complete the work comfortably.
Have the yard securely support the boat. Isolate the starting batteries and independently support the engine and saildrive before releasing their mountings.
- Obtain the correct diaphragm kit and check whether it includes the necessary gaskets, O-rings, fasteners and fitting instructions.
- Remove access panels and photograph hose, cable and mounting positions before disconnecting anything.
- Drain the saildrive oil into a clean container and inspect it for milkiness, water or metallic debris.
- Remove the propeller and any anode or rope cutter that obstructs withdrawal, following their own dismantling instructions.
- Disconnect the cooling-water hose, gear cable and other connections needed for movement. Disconnect exhaust, fuel or electrical connections only where the required engine movement makes this necessary.
Mark engine-mount positions and keep any shims in their original locations. Use proper lifting points and a controlled lifting arrangement. Do not rely on a jack pressing against an unsupported sump.
Separate the drive
Follow the workshop manual's dismantling sequence. Depending on the installation, the engine moves forward, the drive moves aft, or both move slightly to disengage the input shaft. Some designs require the drive housings to be separated to release the diaphragm.