How do I remove and refit the saildrive seal on a Beneteau Oceanis 38?
The rubber around the saildrive on my Beneteau Oceanis 38 is lifting away from the hull. How do I tell whether this is just the outside skirt or the main seal, and what is involved in removing and refitting it?
Answer
First identify the seal: a lifting rubber fairing beneath the hull usually needs rebonding or replacement, while replacing the watertight diaphragm inside requires dismantling the saildrive installation. On a Beneteau Oceanis 38, check the drive model before ordering parts or undoing anything, as the engine badge alone does not identify the seal arrangement.
Identify the rubber component
Many Oceanis 38s have a Yanmar engine and saildrive, but equipment varies with build year and later replacements. Find the identification plate on the saildrive gearbox and record its model and serial number; photograph the installation and obtain the matching workshop procedure.
- External fairing: a relatively thin rubber sheet bonded to the underside of the hull around the leg. It smooths water flow and covers the opening; it is not the main watertight barrier.
- Main diaphragm: the substantial rubber assembly clamped between the drive and its mounting structure inside the boat. Some Yanmar drives have inner and outer diaphragms with a water sensor between them.
- Propeller-shaft seals: seals in the lower gearcase. These need a separate repair, usually investigated when gear oil contains water or oil escapes around the propeller shaft.
Inspect the diaphragm for cracking and swelling, check the clamps for damage and look for a recorded replacement date. The replacement interval comes from the drive manual, not Beneteau's hull model. Volvo shaft-seal advice about greasing and burping does not apply to a saildrive diaphragm.
Repairing the external fairing
With the boat ashore, check that the rubber remains flexible and that only the bond between adhesive and hull has failed. A sound skirt can often be rebonded; replace it if it has split, hardened or lost its shape.
- Photograph its position, then peel it away carefully, using a plastic scraper where necessary.
- Remove old adhesive and loose antifouling from the bonding area without gouging the hull or damaging the leg coating.
- Prepare the hull and rubber with the cleaner, primer and adhesive specified for the fairing kit. Generic silicone is a poor substitute.
- Dry-fit the skirt, apply adhesive as directed and hold it evenly against the hull with suitable temporary support.
- Allow the full specified curing time before launching, taking yard temperature into account.
Do not bond the skirt tightly to the leg unless the fitting instructions require it: the installation must allow for engine movement. Use aluminium-compatible saildrive antifouling on the leg and keep paint off the anodes.
Removing the main diaphragm
Haul out, isolate the batteries and support the engine and saildrive independently with rated lifting equipment before releasing mounts or diaphragm retainers.
Access through the aft cabin and companionway area can dictate how much dismantling is needed. Remove access panels first and establish the withdrawal distance before disconnecting the engine.