How do I remove and refit the saildrive seal on a Jeanneau Sun Odyssey 36i?

First confirm the transmission fitted to your Sun Odyssey 36i: many have a Yanmar engine with a conventional propeller shaft, which needs a different seal replacement procedure from a saildrive. If yours has a saildrive, replacing the main hull diaphragm means hauling out, supporting the machinery and dismantling the drive to its model-specific workshop instructions.

Identify the drive and seal

Start at the engine and follow the transmission aft. A shaft installation has a coupling and a propeller shaft running through a stern tube. A saildrive has a gearbox above a broad rubber diaphragm, with an aluminium leg passing down through the hull. The boat model alone cannot identify the fitted equipment, especially after an engine replacement.

Record the engine and transmission model and serial numbers before ordering parts. A Yanmar engine alone does not tell you which drive or seal kit you need.

• External saildrive fairing: the thin rubber flap glued beneath the hull. It smooths water flow but is not the watertight hull seal.
• Main saildrive diaphragm: the substantial rubber assembly clamped inside the boat. This forms the watertight barrier.
• Propeller-shaft seal: a rubber sleeve or mechanical seal around a horizontal shaft. Saildrive instructions do not apply.

A peeling external flap does not automatically mean the main diaphragm needs replacing. Check the diaphragm's recorded installation date against the replacement interval specified for the fitted drive.

Prepare access and machinery supports

For a main diaphragm replacement, obtain the workshop manual and a complete seal kit matched to the drive serial number. Yanmar and Volvo Penta arrangements differ in diaphragm construction, sealing rings, fasteners and any water-detection system.

Have the boat securely supported ashore. Isolate the batteries and support the engine and drive independently before releasing mounts or retaining bolts.

On the 36i, inspect access through the companionway engine enclosure and adjacent removable panels before starting. Establish whether the drive can be lifted inside or must be withdrawn below. This determines the clearance needed beneath the hull.

1. Photograph hose routing, cable brackets, mounting positions and the existing diaphragm orientation.
2. Drain the saildrive oil into a clean container and inspect it for water or metallic debris.
3. Disconnect the gear cable, cooling-water connections and any sensor wiring required by the manual. Label each connection.
4. Arrange a rated lifting beam or hoist and suitable supports. Do not rely on a jack pressing against the sump.

Remove drive and replace diaphragm

The usual sequence is to separate the engine from the saildrive, release the diaphragm retaining ring and withdraw the drive assembly. Some designs require further separation of the upper and lower drive housings to change the diaphragm. Follow the specified sequence before undoing those joints.