How do I remove and refit the saildrive seal on a Najad 361?
I want to replace the rubber seal around the saildrive on my Najad 361. What needs disconnecting, how do I separate the drive from the engine, and what should I check before refitting it?
Answer
Replacing the main saildrive diaphragm on a Najad 361 means hauling out, supporting the engine and saildrive separately, and dismantling the drive far enough to fit the correct diaphragm. Read the saildrive identification plate first: the boat model alone does not establish the seal kit, dismantling sequence or tightening torques, especially if the engine has been replaced.
Identify the seal and drive
Three different parts are commonly called a saildrive seal:
- Main rubber diaphragm: the substantial rubber membrane clamped between the saildrive and the hull mounting bed; this keeps seawater out of the boat.
- External fairing skirt: the thin rubber flap bonded beneath the hull around the leg; this smooths water flow but does not keep the boat watertight.
- Propeller-shaft seals: the oil seals behind the propeller; replacing these is a different job.
This procedure covers the main diaphragm. Check whether your installation has a Volvo Penta 120S-family drive or another model, and record its full designation and serial number. Obtain the matching workshop instructions and diaphragm kit before dismantling. Volvo Penta commonly specifies replacement every seven years for its conventional saildrive diaphragms; check the instructions for your drive and any recorded replacement date.
A Volvo rubber seal on a conventional propeller shaft is a different component. Advice about greasing and burping that seal does not apply to the saildrive diaphragm.
Prepare access and machinery supports
Before releasing engine mounts or saildrive fasteners, have the boat securely supported ashore, isolate the batteries and put rated lifting equipment in place.
Access dictates the work. On a Najad 361, inspect the space behind and beside the engine to establish whether it can slide forward within the compartment or must be lifted out. Leave enough room for the input shaft to disengage fully and for the drive to lift clear of its hull aperture.
- Photograph the installation, label connections and record the engine-mount positions.
- Remove the propeller and any components that obstruct withdrawal, following their specific instructions.
- Drain the saildrive oil into a clean container and check for water, milkiness or metallic debris.
- Disconnect the cooling-water hose, gear cable and any brackets or wiring that prevent movement; cap open connections.
- Support the engine and drive separately, then release the necessary mounts and coupling-housing fasteners in the workshop-manual sequence.
Arrange an engine hoist or properly rigged lifting beam, a separate support for the drive, a torque wrench and suitable oil-catching trays. Do not use the diaphragm clamping ring as a lifting point.
Separate drive and replace diaphragm
Withdraw the engine and drive squarely from one another. If they remain stuck after the specified fasteners have been removed, check for concealed bolts, locating dowels, brackets and load on the input shaft. Corroded splines can resist separation. Do not hammer the aluminium housing or force screwdrivers between mating faces.