Part of the Yanmar Repair Manuals.
Split the upper case on an SD40 or SD50 and the first thing you learn is that nothing goes back together by feel: gear position lives in shim stacks, and the cone clutch only holds if the bearing gaps are right. This 69 page Yanmar service manual, publication M2215-04E140, is the factory procedure for getting every one of those numbers.
It covers the SD40-3, SD50-3, SD40-4, SD50-4, SD40-4T and SD50-4T sail drive units used with the 3JH3CE, 3JH4CE, 4JH3CE, 4JH4CE and 4JH3-TCE engines. Inside are full disassembly and reassembly sequences for the upper and lower cases, shim selection with the measurements and calculations written out, gear backlash and dye pattern checks, shift lever adjustment, and the tightening torque table for the shaft nuts and bolts.
It is a bookmarked PDF, so the replacement criteria and torque figures travel with you, whether the unit is on the bench in pieces or bolted back into the boat.
What's Inside This Yanmar SD40–SD50 Series Manual
| System | Pages | Key Topics |
|---|---|---|
| History of Correction | 2 | Manual Name |
| For Safety | 5-10 | Safety Labels, Service Area, Work - Wear (Garments), Tools, Fastener Torque, Further Precautions |
| General | 11-29 | Specifications, Exterior View, Sectional View, Criteria for Replacing Parts, Route of Cooling Water and Lubricating Oil, Lubricating Oil, Disassembly and Reassembly, Special Tools |
| Disassembly | 30-47 | Disassembling the Upper Case (Removal of the Unit, Disassembling the Unit), Disassembling the Lower Case (Removal of Unit) |
| Reassembly | 48-49 | Reassembling the Bearing for Lower Case (Needle Bearing, Taper Roller Bearing Outer Race), Reassembling the Bearings of Shaft (Propeller Shaft, Drive Shaft) |
| Shim Adjustment (Gear Backlash Adjustment) | 50-56 | Location of Adjustment Shims, Measurement of the Dimensions of the Cases (Upper Case, Lower Case) |
| Adjustment of Bearing Assembly Gap | 57-60 | Upper Gear Bearing (Measurement of the Dimension of the Bearing, Calculation of the Shim Thickness) |
| Adjustment of the Gear Backlash | 61-62 | Upper Gear, Lower Gear |
| Adjustment of the Gear Dye Pattern | 63-64 | Upper Gear, Propeller Shaft |
| Adjustment of the Shift Lever | 65-66 | Measurement of the Dimensions (Shift Lever Bolt, Shifter Pin Position), Calculation of the Shim Thickness, Caution of Reassembly |
| Tightening Torque for Nuts and Bolts | 67 | - |
| Colophon | 68 | First Edition, Published by, Copyright |
Quick Reference Specifications
| Specification | Value | Page |
|---|---|---|
| Tightening torque for propeller shaft nut | 166.6±5.0 N-m (17±0.5 kgf-m) | p. 67 |
| Tightening torque for drive pinion end nut (left screw) | 147±5.0 N·m (15±0.5 kgf・m) | p. 67 |
| Tightening torque for pinion shaft assembly bolt | 73.5±3.0 N·m (7.5±0.3 kgf-m) | p. 67 |
| Needle bearing (A) (K24 x 28 x 17) replacement interval | Every 1500 hours | p. 14 |
| Needle bearing (B) replacement interval | Every 1500 hours | p. 14 |
| O-ring replacement criteria | Disassembly | p. 14 |
| Diaphragms (A) & (B) replacement criteria | Hair cracks | p. 14 |
| Lubricating oil type (API service grade) | GL4 or higher | p. 11 |
| Lubricating oil type (SAE grade) | SAE 80W-90 | p. 11 |
| Shift lever adjustment clearance | 0.2~0.4 mm | p. 65 |
| Reduction ratio (Ahead/Astern) | 2.32 | p. 11 |
| Allowable speed at Input shaft | 4000 min-1 | p. 11 |
Yanmar SD40–SD50 Series Common Problems This Manual Covers
Cone clutch slips under load
Loss of drive or weak engagement in ahead or astern usually traces to worn or glazed cone clutch surfaces. Getting to the clutch means opening the upper case in the correct order, and the Disassembly section documents the removal and teardown sequence for the whole unit.
Manual Section: 2 Disassembly p. 30Vertical shaft play causes clutch slip
Excess up and down free play in the upper shaft reduces cone clutch contact, and no amount of new clutch parts fixes it until the bearing gaps are set. The manual shows how to measure the bearing dimensions and calculate the shim thickness to close that play.
Manual Section: 5 Adjustment of Bearing Assembly Gap p. 57Gear whine after bearing replacement
Fit new bearings or gears without resetting the shims and the mesh runs noisy and wears fast. The shim adjustment section locates every adjustment shim and walks through measuring the upper and lower cases to select the right stack.
Manual Section: 4 Shim Adjustment (Gear Backlash Adjustment) p. 50Oil seals leaking, water in gear oil
Lip hardening and hair cracks in the oil seals let water into the lubricating oil and shorten the life of everything downstream. The General section's replacement criteria call for new seals every 1000 hours or 2 years, whichever comes first.
Manual Section: 1 General p. 11Needle bearings flaking at high hours
Needle flaking or lost needles show up in high hour units, and the manual sets a 1500 hour replacement interval for both needle bearings. The Reassembly section covers seating the needle bearing and taper roller bearing outer race in the lower case correctly.
Manual Section: 3 Reassembly p. 48Drive will not stay in gear
Inconsistent shifting or a drive that drops out of gear often comes down to shift lever setup rather than the clutch itself. The manual gives the shift lever bolt and shifter pin measurements, the shim thickness calculation, and the reassembly cautions.
Manual Section: 8 Adjustment of the Shift Lever p. 65Frequently Asked Questions
Which sail drive models does this manual cover?
It covers the Yanmar SD40-3, SD50-3, SD40-4, SD50-4, SD40-4T and SD50-4T sail drive units (also cataloged as SD40/SD40-4T and SD50/SD50-4T), used with the 3JH3CE, 3JH4CE, 4JH3CE, 4JH4CE and 4JH3-TCE engines.
Does it list the propeller shaft nut torque?
Yes. The Tightening Torque for Nuts and Bolts section gives 166.6±5.0 N·m (17±0.5 kgf·m) for the propeller shaft nut, 147±5.0 N·m for the drive pinion end nut (left hand thread), 73.5±3.0 N·m for the pinion shaft assembly bolt, and 29.4±2.0 N·m for the M6 anti-corrosive zinc bolts. p. 67
Can I fix a slipping cone clutch with this manual?
It covers the work behind the fix: the Shim Adjustment section shows where every adjustment shim sits and how to measure the cases and calculate shim thickness for the clutch shaft, pinion shaft, drive shaft and propeller shaft, followed by gear backlash and dye pattern checks. p. 50
Are replacement intervals for seals and bearings included?
Yes. The Criteria for Replacing Parts table in the General section specifies oil seals every 1000 hours or 2 years, needle bearings every 1500 hours or on evidence of flaking, O-rings at every disassembly, and diaphragms every 2 years or when hair cracks appear. p. 11
How will I receive this Service Manual?
You get a 69-page searchable PDF that downloads instantly after checkout. Open it on your laptop, tablet, or phone, and bring it right to the shop floor.
Is this Yanmar SD40–SD50 Series Service Manual printable?
Yes. The PDF has no DRM restrictions, so print any page or section you need for your shop. Works with any standard printer.
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