Part of the Yanmar Parts Manuals.
The crank is out, the machine shop has measured the journals, and the next question is whether Yanmar lists an undersize bearing for this block. This catalog answers it. Publication Y00B4102 covers the 3TNA72L-UBA and 3TNA72L-UBA/B three-cylinder diesels, whether the engine is still bolted into whatever it powers or stripped bare on a stand.
Its 34 pages step through sixteen exploded figures with numbered parts lists: cylinder block, gear housing, flywheel housing and oil sump, cylinder head and bonnet, camshaft, crankshaft and pistons, the lubrication oil and cooling water systems, fuel injection device, fuel pipe, governor, starting motor, generator, and an optional tool and gasket set.
Every callout ties a part on the diagram to its Yanmar part number, including rebuild sizes such as 0.25 and 0.5 oversize pistons, so the order you place matches the engine you measured. The PDF downloads immediately after purchase and prints cleanly for the bench.
What's Inside This Yanmar 3TNA72L-UBA, 3TNA72L-UBA/B Parts Manual
| System | Pages | Key Topics |
|---|---|---|
| Engine | 1-2 | Cylinder Block Assy, Main Bearing, Thrust Bearing, Camshaft Bush, Cylinder Head Gasket, Gasket, Joint PT1 |
| Cylinder Block | 3-4 | Gear Housing Assy, Housing Cover Assy, Oil Seal HTC456208, Knock Pipe, Cover, Pump Cover Gasket, Gasket, Lub. Oil Supply Cap |
| Gear Housing | 5-6 | Lub. Oil Sump Assy, Oil Sump Spacer, Oil Seal Case Assy, Oil Seal, Flywheel Housing, Flywheel Cover Cap |
| Flywheel Housing & Oil Sump | 7-8 | Cylinder Head Assy, Suction Valve, Exhaust Valve, Valve Spring, Spring Retainer, Valve Stem Seal, Valve Cap, Nozzle Protector |
| Cylinder Head & Bonnet | 9-10 | Air Cleaner Support, Support Felt, Air Cleaner, Case, Air Cleaner Element, Dust Pan, Retainer, Air Intake Pipe |
| Suction Manifold & Air Cleaner | 11-12 | Silencer Gasket, Gasket, Silencer, Silencer Stay, Exhaust Manifold, Exhaust Manifold Gasket |
| Exhaust Manifold & Silencer | 13-14 | Camshaft Assy, Camshaft Gear, Thrust Bearing, Push Rod, Tappet, Fuel Cam Bearing, Fuel Injection Pump Cam Assy, Idle Gear Retainer |
| Camshaft & Driving Gear | 15-16 | Crankshaft Assy, Crankshaft Gear, Crankgear, V-pulley, Flywheel Assy, Ring Gear, Piston w/ Rings, Ring Set |
| Crankshaft & Piston | 17-18 | Lub. Oil Pump Assy, Lub. Oil Pump Gasket, Lub. Oil Dipstick, Dipstick Guide, Oil Filter Bracket, Bracket Gasket, Gasket, Lub. Oil Filter |
| Lubrication Oil System | 19-20 | Cooling Water Pump Assy, Cw Pump Assy, Cooling Water Pump Gasket, V-belt, Cooling Water Pump V-pulley, Thermo Switch, Gasket, Thermostat Cover |
| Cooling Water System | 21-22 | Fuel Injection Pump Assy, Plunger w/ Barrel, Retainer, Plunger Spring, Delivery Valve w/ Seat, Delivery Valve Spring, Delivery Valve Holder, Delivery Gasket |
| Fuel Injection Device | 23-24 | F.feed Pump Gasket, Gasket, Feed Pump, Fuel Feed Pump Assy, F.o Strainer Assy, Taper Valve, Taper Valve Spring, Lever |
| Fuel Pipe | 25-26 | Governor Case, Governor Case Gasket, Gasket, Governor Case Cover, Link Color, Link, Governor Weight Assy, Governor Sleeve |
| Governor | 27-28 | Starter 12V- .0W, Retainer, Yoke Assy, Armature Assy, Bearing, Starter Clutch, Starter Pinion, Shaft |
| Starting Motor | 29-30 | Generator, Collar, Plate Assy, Stator, Coupler, Flywheel Assy, Belt Adjuster |
| Generator | 31-32 | Flex Horn, Gasket Set, Cylinder Head Gasket, Bonnet Gasket, Int.manifold Gasket, Silencer Gasket, Exhaust Manifold Gasket, Cooling Water Pump Gasket |
| Tool & Gasket Set Optional | 33-34 | Overview, Parts List, Brush, Gasket, Liquid, Cylinder Head, Rocker Cover, Oil Pan |
Every system also includes overview.
Quick Reference Specifications
| Specification | Value | Page |
|---|---|---|
| Main Bearing Undersize | 0.25 (unit not specified) | p. 2 |
| Piston W/Ring Oversize | 0.25 (unit not specified) | p. 16 |
| Ring Set Oversize | 0.25 (unit not specified) | p. 16 |
| Bearing Pin Undersize | 0.25 (unit not specified) | p. 16 |
| V-Belt FM Length | 36.5 (unit not specified) | p. 20 |
| Fuel Pipe Diameter x Length | 12mm x 400mm | p. 24 |
| Governor Link Length (No Color) | 88.8 (unit not specified) | p. 26 |
| Governor Link Length (White) | 88.6 (unit not specified) | p. 26 |
| Starter Motor Rating | 12V-1.0W | p. 28 |
Yanmar 3TNA72L-UBA, 3TNA72L-UBA/B Common Problems This Manual Covers
White smoke and rough running
Worn or contaminated injector nozzles spray poorly and show up as white smoke and rough combustion under load. The Fuel Injection Device parts list breaks the injector down to nozzle assembly, nozzle spring, valve with seat and spacer, so you can order internals instead of complete assemblies.
Manual Section: Fuel Injection Device p. 23Overheating and coolant loss
A failing water pump, stuck thermostat or slipping belt will push this engine hot fast. The Cooling Water System figure lists the pump assembly, thermostat and its gaskets, V-belt, pulley, fan and thermo switch with their Yanmar part numbers.
Manual Section: Cooling Water System p. 21Low oil pressure warnings
Contaminated oil and a tired pump eventually take out bearings. The Lubrication Oil System section identifies the oil pump assembly, filter and bracket gaskets, strainer O-ring, oil pressure relief valve and the oil pressure switch, all the parts you replace before chasing pressure elsewhere.
Manual Section: Lubrication Oil System p. 19Blowby and oil consumption
Worn bores and rings mean a rebore, and this catalog carries the numbers for it: pistons with rings in 0.25 and 0.5 oversize, matching ring sets, connecting rod bearings, a 0.25 undersize crankpin bearing and piston pin bushes.
Manual Section: Crankshaft & Piston p. 17Hard starting and weak compression
Leaking valves, worn guides and hardened stem seals cost compression and make cold starts a battle. The Cylinder Head & Bonnet parts list covers suction and exhaust valves, springs, guides, stem seals, rocker gear and the glow plugs and their connector.
Manual Section: Cylinder Head & Bonnet p. 9Fuel starvation after sitting
A clogged strainer element or a dying feed pump will starve the injection pump and mimic bigger problems. The Fuel Pipe section lists the fuel feed pump assembly, strainer assembly with element and taper valve, plus the joints, gaskets and clamps for the lines.
Manual Section: Fuel Pipe p. 25Slow or intermittent cranking
Starters and their connections wear out on small diesels that live outdoors, and slow cranking alone can stop one from firing. The Figure 14 Starting Motor parts list gives the correct replacement part numbers for the starter fitted to these engines.
Manual Section: Figure 14 Starting MotorFrequently Asked Questions
Which engines does this parts catalog cover?
It is Yanmar publication Y00B4102 for the 3TNA72L-UBA and 3TNA72L-UBA/B three-cylinder diesel engines. It documents the engine itself, so it applies regardless of what the engine is installed in.
Is this a service manual with repair procedures and torque specs?
No. This is the factory parts catalog: sixteen exploded-view figures, each paired with a numbered parts list and Yanmar part numbers. Use it to identify and order correct parts, not for step-by-step disassembly or adjustment procedures.
Does it list oversize pistons and undersize bearings for a rebuild?
Yes. The Crankshaft & Piston section lists pistons with rings and ring sets in 0.25 and 0.5 oversize plus a 0.25 undersize crankpin bearing, and the Cylinder Block parts list includes a 0.25 undersize main bearing. p. 17
Does it break down the fuel injection pump?
Yes. The Fuel Injection Device section lists injection pump internals including the plunger with barrel, delivery valve with seat, holder, shim pack, tappet assembly and rack, along with the complete injector and injection pipes. The separate Fuel Pipe section covers the feed pump and fuel strainer. p. 23
How quickly can I access this Yanmar 3TNA72L-UBA manual after buying?
A 34-page Parts Catalog in searchable PDF format (1 MB), available the moment you complete checkout. View on computer, tablet, or phone, with no shipping wait.
Am I able to print pages from this Yanmar 3TNA72L-UBA manual?
Absolutely. No DRM or copy protection. Print the whole manual or just the pages you need. Any home or office printer works.
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