Saildrives combine a gearbox, underwater leg, propeller shaft, hull seal and corrosion-protection system. All five need attention.
Every inspection cycle
- Check lubricant level and appearance using the model method.
- Inspect for oil loss at the upper housing and propeller-shaft seals.
- During haul-out, drain or sample from the lowest point to reveal water.
- Inspect and measure anodes, noting the exact alloy and rate of consumption.
- Repair coating damage with products approved for aluminium drives.
- Clear cooling-water inlets without damaging the coating.
- Remove the propeller as instructed and inspect for fishing line.
- Inspect folding or feathering hubs and renew lubricant as specified.
- Check diaphragm condition, clamping hardware and leak sensor.
Milky oil suggests water but air entrainment can also cloud some lubricants. Allow a sample to settle and use pressure or vacuum testing to locate leakage rather than replacing seals blindly.
Rapid anode loss suggests abnormal galvanic or stray-current conditions. An anode that never wastes can be the wrong alloy, coated, electrically disconnected or unnecessary in that exact circuit. Do not add bonding wires or extra anodes without understanding the manufacturer’s isolation design.
An older Yanmar manual for SD20 and SD50-family drives requires approved coating, warns against copper or tin paint on the aluminium leg, specifies anode replacement by condition or interval, diaphragm inspection every two years and diaphragm replacement every five years. This is a useful example of why the serial-specific manual matters, not a universal schedule for all saildrives.