Saildrives

Manufacturer: Yanmar
Description: Saildrive Unit
Model: SD20
Manual: File:SD20 Operations Manual 2009.pdf
Parts catalog: File:SD20 Part Catalog.pdf
O-Ring parts diagram: File:SD20 O-rings Parts Diagram .pdf
Service Bulletin - Taper pin: File:SD20 Taper Pin Bulletin.pdf

Saildrive Oil
Oil specifications: 80W90W gear oil (API GL-4 or GL-5)
Oil capacity: 700ml
Oil change interval: Every 250 hours of operation or annually (whichever comes first)

Procedure to change oil in the water:

1. Using a pump with a small tube remove as much oil as possible
   
2. Refill oil to full capacity (bottom of dipstick)
3. Run engine 5 minutes
   
4. Using a pump with a small tube remove as much oil as possible
   
5. Refill oil to full capacity (bottom of dipstick)
   

(This will replace over 75% of the oil)

Outer diaphragm and secondary inner diaphragm
Replacement Guidelines: Inspect every 2 year and replace every 5 years
Common Practice: Monitor condition and test the water penetration sensor
Recommendations: Pacwest in San Diego does not recommend changing the diaphragms unless there is visible damage or water has penetrated the outer diaphragm. These diaphragm almost never fail. I have read this from other sources who make the same recommendation.

Propeller Shaft Grooves
It is an issue that they Gori propellers installed on a SD20 saildrive will form grooves over time which will result in sea water penetration. Periodic repositioning of the seals using shims allow longer life from the propeller shafts.

Notes:
Blown seals: The SD20 is susceptible to blowing the seals if the oil is filled too high. Many have added a vent line to the top of the filler cap. Without the vent, only fill the saildrive oil to the bottom of the dipstick

Sheared tapper pin repair: External Link

Grooves worn into the propeller shafts