Before you tear into your marine drive, grab this 86-page Yanmar SD20, SD50 Operation Manual PDF (OEM #0ASDM-G00101) covering complete factory maintenance procedures for the SD50-4T sail-drive variants. Inside, you get detailed periodic schedules, clear exploded views for component identification, and high-quality system wiring diagrams. Open the guide to find exact procedures for everything from new break-in routines to checking the instrument panel alarm system and fitting a fixed propeller. Inspect and lap the cone clutch every 500 hours, and make sure you torque the SD20 propeller nut to exactly 60 to 70 N·m before launching. A failed drive leaves you stranded on the water with a hefty tow bill. Download this bookmarked file straight to your phone, find the right spec, and keep your vessel moving.
What's Inside This Yanmar SD20, SD50, SD50-4T Manual
| System | Pages | Key Topics |
|---|---|---|
| Introduction | 5-6 | Sail-Drive Models, Engine Models, Engine and Sail-Drive Combinations |
| Safety | 7-12 | Safety Precautions (Before You Operate, During Operation and Maintenance) |
| Product Overview | 13-18 | Overview (Owner / Operator Responsibilities, New Sail-Drive Break-In, Dealer / Distributor Responsibilities, Component Identification, Galvanic Corrosion, Corrosion Control, Shore Power, Underwater Drive Coating) |
| Before You Operate | 19-28 | Propeller Selection (Recommended Propeller Size, Fitting a Fixed Propeller), Lubricating Oil (Filling with Lubricating Oil - SD20, SD50 and SD50-4T) |
| Sail-Drive Operation | 29-34 | Remote Control Device Check, Sd20, Sd50 / Sd50-4T, Engine Cooling Water (Sd20) |
| Periodic Maintenance | 35-56 | Tightening Fasteners, Torque Charts, Periodic Maintenance Table, When the Vessel Is Out of the Water, Perform the Following:, Periodic Maintenance Procedures |
| Specifications | 57-58 | Reduction Gear System, Direction of Rotation, Reduction Ratio, Lubricating Oil Capacity, Dry Weight, Remote-Control Device |
| System Diagrams | 59-86 | Maintenance Log |
Quick Reference Specifications
| Specification | Value | Page |
|---|---|---|
| SD20 | ||
| Propeller Nut Tightening Torque | 60 to 70 N·m (44 to 52 lb-ft) | p. 21 |
| Dry Weight | 30 kg (66 lb) | p. 57 |
| Reduction Ratio (Ahead) | 2.64 | p. 57 |
| SD50, SD50-4T | ||
| Propeller Nut Tightening Torque | 80 to 100 N·m (59 to 74 lb-ft) | p. 21 |
| Lubricating Oil Capacity (Long-Reach Unit, Extension 100) | 2.45 L (2.6 qt) | p. 23 |
| All Models | ||
| Cone Clutch Inspection/Lapping Interval | Every 500 hours | p. 40 |
| Cone Clutch Replacement Interval | Every 2000 hours | p. 40 |
| Rubber Diaphragm Inspection Interval | Every Year | p. 40 |
| Rubber Diaphragm Replacement Interval | Every 5 Years | p. 40 |
| SD20, SD50, SD50-4T | ||
| Lubricating Oil Capacity (Standard Unit) | 2.2 L (2.3 qt) | p. 23 |
| SD50 | ||
| Dry Weight | 39 kg (86 lb) | p. 57 |
| SD50-4T | ||
| Dry Weight | 41 kg (90 lb) | p. 57 |
Yanmar SD20, SD50, SD50-4T Common Problems This Manual Covers
Yanmar SD50 propulsion slips in forward or astern under load even at relatively low hours p. 40
Inspect the cone clutch assembly for wear and perform lapping. Check the maintenance schedule on page 40 to verify inspection and lapping occur every 500 hours. Replace the entire cone clutch mechanism every 2000 hours if slipping persists after adjustment.
Manual Section: Inspecting and / or Replacing the Cone-ClutchGearbox lubricating oil appears milky indicating seawater ingress and lower-unit seal failure p. 23
Drain the contaminated fluid and inspect lower-unit propeller shaft seals for grooving. Fill the standard unit with 2.2 L (2.3 qt) of fresh lubricating oil as specified on page 23. Test the drive in the water and check for leaks.
Manual Section: Lubricating OilWarning buzzer sounds and rubber seal alarm lamp triggers during normal operation p. 40
Inspect the seal sensor and the area between diaphragm A and B for seawater. Check the maintenance schedule on page 40 and replace the rubber diaphragm and rubber protection parts every 5 Years. Clean the sensor contacts and reset the panel.
Manual Section: Instrument Panel Alarm System CheckFolding propeller opens improperly or feels extremely loose on the splined shaft p. 21
Remove and inspect the blade-fixing pins for severe wear. Reinstall the propeller assembly and torque the propeller nut to 60 to 70 N·m (44 to 52 lb-ft) for standard drives as detailed on page 21. Verify smooth opening action manually.
Manual Section: Before You OperateFrequently Asked Questions
What are the torque specifications for the propeller shaft nut on YANMAR SD20 and SD50/SD50-4T sail-drives?
For the SD20, the propeller shaft nut (M16) should be tightened to 60 to 70 N·m (44 to 52 lb-ft). For the SD50 and SD50-4T, the propeller shaft nut (M20) requires a tightening torque of 80 to 100 N·m (59 to 74 lb-ft). Refer to page 21 for the propeller fitting diagram and torque table.
What do the alarm indications mean on a YANMAR SD20 or SD50 sail-drive instrument panel?
On the B-Type instrument panel, key alarm indications include the Battery Low Charge Alarm, Sail-Drive Seal Warning Lamp, Engine Oil Low Pressure Lamp, and Coolant High Temperature Alarm. For C-Type panels, additional indicators like Fuel Filter Warning Lamp and Seawater Insufficient Flow Alarm are present. These lamps, along with a warning buzzer, indicate specific operational issues.
Why might my YANMAR SD50 sail-drive be slipping in forward or astern?
Slipping in forward or astern on an SD50 sail-drive can be caused by running the Sail-Drive for long periods at low RPM while engaged. This can lead to premature wear of the cone clutch. Periodic inspection and maintenance of the cone clutch are necessary.
What is the lubricating oil capacity for the YANMAR SD20, SD50, and SD50-4T sail-drives?
The standard unit oil capacity for SD20, SD50, and SD50-4T is 2.2 L (2.3 qt). For long-reach units, the SD20 requires 2.5 L (2.6 qt), while the SD50/SD50-4T requires 2.35 L (2.5 qt) for Extension 58 and 2.45 L (2.6 qt) for Extension 100. Always confirm the capacity using the oil capacity nameplate.
How will I receive this Yanmar SD20, SD50, SD50-4T Operation Manual?
Immediate download of the complete 86-page searchable Operation Manual. Access it on any device, from a laptop at your desk to a phone in the field.
Can I print specific sections of this manual?
Absolutely. No DRM or copy protection. Print the whole manual or just the pages you need. Any home or office printer works.
Are electrical wiring diagrams included in this Yanmar SD20, SD50, SD50-4T?
Included. The Yanmar SD20, SD50, SD50-4T Operation Manual provides a wiring diagram for the electrical system.
Document Quality
This document is a scanned PDF with an OCR text layer, allowing you to search and copy text throughout. The main text is crisp and consistently readable, though not as sharp as a native digital file. Diagrams and illustrations are raster images, but their labels are clear and legible at typical zoom levels. All pages are clean and free from scan artifacts, stains, or skewed content. You will find several "This Page Intentionally Left Blank" filler pages distributed throughout the document.
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