Saildrive vs shaft drive: what changes for the propeller

Around a third of the fitments in our database are saildrives — the Volvo and Yanmar legs behind most modern production yachts and nearly all production catamarans. For propeller purposes, the differences from a shaft installation are practical and specific.

The fitting is completely different

A shaft propeller mounts on a tapered shaft with a key and nut; sizes quote shaft diameter and taper. A saildrive propeller mounts on a splined stub — the spline count and profile must match your drive model exactly (Volvo 110S/120S/130S/150S and Yanmar SD20/25/60 families differ). This is why we ask for the drive model, and why the Autoprop APS series exists as dedicated variants.

Anodes and galvanic care

Saildrive legs are aluminium living underwater near a bronze propeller — anode discipline matters. Saildrive props carry their own anode arrangements, and leg anodes must be maintained on schedule. It's routine, but it's non-negotiable.

Water flow and clearance

• Saildrives put the prop in clean, undisturbed water ahead of the rudder — ideal for self-pitching blades.
• Clearance to the hull is fixed by the leg geometry; diameter ceilings are usually tighter than shaft boats.
• Twin saildrive cats want handed pairs (LH & RH) for symmetric handling — standard practice in our catamaran work.