The Yanmar 3TNM68 engine is a small but mighty diesel engine. Yanmar designed it for compact equipment where size and weight matter. You find it in ride-on rice transplanters, small mowers, compact generators, and light construction gear. It is not a big engine, but it does its job well. And when you know what to look for, it can serve you for a long time.
At Yutian Machinery, we have seen plenty of these little engines come and go. Some were well cared for. Some were not. Let me walk you through what makes this engine tick, where it is used, and how to buy one without getting burned.
What Is the Yanmar 3TNM68?
The 3TNM68 is a three-cylinder, water-cooled diesel engine. It belongs to Yanmar’s TNM series, which the company launched around 2015. The engine is compact and lightweight. It weighs about 132 kilograms (or around 90 kg for some packaged versions). You can hold it on a small pallet.
Here are the key numbers.
| Specification | Detail |
|---|---|
| Engine Type | 4-cycle, vertical, water-cooled diesel |
| Number of Cylinders | 3 |
| Bore and Stroke | 68 mm × 72 mm |
| Displacement | 0.784 liters (784 cc) |
| Combustion System | Indirect injection (IDI) |
| Aspiration | Naturally aspirated (no turbo) |
| Maximum Power | Up to 14.7 kW (about 20 horsepower) at 3,600 rpm |
| Direction of Rotation | Counterclockwise (viewed from flywheel end) |
| Starting System | 12V electric starter motor |
| Lubrication | Liquid-cooled with a radiator |
| Cooling | Liquid-cooled with radiator |
| Weight | Approximately 132 kg |
Some sources list the maximum output at 14.1 kW, others at 14.7 kW. The difference comes from how the engine is tuned for different applications. Either way, it is a 20-horsepower class engine.
The engine uses indirect injection, which means fuel is sprayed into a small pre-combustion chamber first. That design makes the engine start more easily in cold weather and run more smoothly at low speeds. It also produces less noise than some direct-injection engines.
What Machines Use the 3TNM68?
This engine is not for big excavators or heavy trucks. It is for small, specialized machines. You find it in:
Agricultural Equipment
- Rice transplanters: The Fulaiwei 2ZG-6DM ride-on rice transplanter uses the 3TNM68-AMW version. That engine produces 12.3 kW at 3,600 rpm and has a 20-liter fuel tank. Other rice planters and harvesters from Japan also use this engine, often with only 300 to 500 working hours. In Japan, they use these machines only a few times a year for planting and harvesting.
- Small tractors and mowers: John Deere’s 2653a fairway mower runs on a 3TNM68 engine. Some owners have reported fuel pump issues, but we will get to that later.
- Walk-behind tractors, sprayers, irrigation pumps: The engine fits anywhere a small, reliable diesel power source is needed.
Light Construction and Industrial Equipment
- Small generators (5-15 kVA): The engine can be configured as a power pack for generator sets. Denyo, Sawafuji, and Toyo Denki have generator models that use this engine.
- Welding machines, air compressors, light construction gear: The 3TNM68 is popular in compact equipment where space is tight and reliability matters.
- Mini excavators: Some small European and Japanese mini excavators use the 3TNM68. Kato 12VXE and IHI Carry 110 are examples.
Other Equipment
- Small utility vehicles: Linhai LH300 CUV uses this engine.
- Marine auxiliary power: Small fishing boats and workboats use it for hydraulic systems and bilge pumps.
The engine comes in different versions for different machines. The base engine is the same, but the intake manifold, exhaust manifold, oil pan, and mounting brackets can differ. For example, a rice transplanter needs a different oil pan shape than a mini excavator. When you buy a used 3TNM68, you need to know which version fits your machine.
The Different Versions of the 3TNM68
Yanmar made the 3TNM68 in several variants. Each one is tuned for a specific application. Here are the common ones.
3TNM68-AMW: Used in rice transplanters. It makes 12.3 kW at 3,600 rpm.
3TNM68-GGE: A general-purpose industrial version. It makes about 9.8 hp at 1,800 rpm, though it can rev much higher. The letter codes tell you about the configuration.
3TNM68-HGE, HGET: These are other industrial versions. The suffix indicates different accessory packages and power ratings.
3TNM68-ASA3: An unused version seen at auction with a US EPA label. This one makes 14.1 kW and was built to meet Tier 4 standards.
3TNM68-AS: A version in the Induspack line, designed for industrial equipment.
3TNM68-GA, HA: Genepack versions for generator applications. These come as complete power packs with radiators and control panels.
Not sure which one you need? The easiest way is to look at your old engine’s model plate. The plate tells you the exact variant. If the plate is missing, take photos of your engine from all angles and show them to a reputable seller. They can match the mounting points and accessory locations.
Emission Standards and Compliance
The 3TNM68 meets modern emission standards. For generators, it meets EU Stage V, which is the current standard for Europe. It also meets standards for lower-regulated countries. For industrial use, the engine can be certified to US EPA Tier 4 and California ARB standards.
What does this mean for you? If you use the engine in a place with strict emission rules, like the European Union or some parts of China and the US, you need a version that meets those rules. A Tier 4 engine may cost more, but it is legal. A cheaper, older engine may not pass inspection. Ask the seller for the emissions label before you buy.
Common Problems and What to Check
The 3TNM68 is a reliable engine, but it has its weak points. I have seen a few issues come up repeatedly. Here they are.
1. Fuel Pump Solenoid Sticking
This is the most common problem with this engine. The fuel pump has a solenoid that controls the fuel shut-off lever. Sometimes the lever inside the pump gets stuck. The engine gets fuel to the injection pump, but no fuel goes past it into the injectors. The engine cranks but does not start. Owners of John Deere 2653a mowers with the 3TNM68 have reported this exact issue.
How to check it: Remove the fuel stop solenoid and look inside. The lever should move freely. If it is stuck, the pump may need cleaning or rebuilding. This is not a simple fix for a beginner. A good seller would have tested for this before listing the engine.
2. Air in the Fuel System
Because the engine is indirect injection, it is sensitive to air in the fuel lines. If you run out of fuel or change the fuel filter, you must prime the system. The operation manual has a priming procedure. If you skip this step, the engine may not start or may run roughly.
3. Fuel Injector and Return Line Issues
The injectors on the 3TNM68 can get dirty or fail over time. When they fail, the engine may run rough, produce white smoke, or lose power. The fuel return pipe and return hose are also wear items. Genuine Yanmar parts are available for these components.
4. Hard Starting in Cold Weather
Indirect injection engines are good at starting in cold weather, but they still need glow plugs or intake air heaters in very cold conditions. If the engine is hard to start when cold, check the glow plug system first.
5. General Wear on Small Engines
The 3TNM68 is a small engine. It works hard for its size. If it were used in a rice transplanter, it may have very low hours. One seller reports that Japanese rice harvesters with this engine have only 300 to 500 total working hours. Those engines are often in good shape.
If the engine were used in a generator running 24/7, the hours could be much higher. Ask about the machine it came from. Low hours and gentle use are your friends.
Buying a Used 3TNM68 – What to Watch For
If you are shopping for a used 3TNM68, here is what I recommend.
Know the history. Ask where the engine came from. Was it on a rice transplanter with 500 hours? Or was it on a generator that ran every day for two years? The difference in wear is huge.
Ask for a cold start video. The seller should be able to send you a video of the engine starting from cold. Watch for white smoke, blue smoke, and how long it takes to start. A little white smoke on a cold day is normal. Blue smoke means oil is burning. Thick black smoke means the fuel system may be off.
Ask about the fuel system. Has the injection pump been serviced? Have the injectors been tested? These are expensive repairs. A seller who can answer these questions is a good sign.
Check the variant. If you need a 3TNM68-AMW for a transplanter, do not buy a 3TNM68-GGE. They may look the same, but the accessories and tuning are different. The seller should tell you exactly which variant they have.
Look for signs of neglect. Oil leaks around the valve cover or oil pan are red flags. Corrosion on the cooling system also is a red flag. A well-maintained engine should be clean and dry.
Ask about the emission rating. If your local rules require Tier 4, make sure the engine has a Tier 4 label. Do not buy an older engine and hope it passes inspection.
Watch for “as-is, no warranty” listings. Some auction places sell everything “as is, where is” with no guarantees. That is fine if you know what you are doing. But for most buyers, a seller who offers at least a short warranty gives you peace of mind.
Why Buy from Yutian Machinery?
At Yutian Machinery, we know the 3TNM68 engine well. We have helped customers find the right Yanmar engine for their transplanters, mowers, and generators.
Here is what we offer.
- We test every engine. Each engine goes through a start-up test. We check for fuel system problems, unusual smoke, and strange noises.
- We verify the variant. We tell you exactly which version you are buying. No guessing.
- We provide videos. You get a cold start video and a running video. You can see the engine for yourself before you pay.
- We give clear information. We tell you where the engine came from and what condition it is in. We also tell you the hours if we know them.
- We offer warranties. A short warranty gives you time to install and test the engine.
- We pack engines properly. Your engine is created for export. We also help with paperwork for customs.
Have questions about the 3TNM68? Not sure if it fits your machine? Contact us. We are happy to help, even if you are just looking.
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- WhatsApp / WeChat: [Your Contact]
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Final Thoughts
The Yanmar 3TNM68 is a small engine with a big reputation. It is not powerful, but it is reliable and fuel-efficient. It fits in places where bigger engines cannot go. A rice transplanter or a compact mower needs an engine that starts every time and does not drink too much fuel. The 3TNM68 fits that bill.
But like any engine, it needs care. Use clean fuel. Change the oil and filters on time. Keep the cooling system clean. And when something feels off, look into it before it becomes a big problem. A stuck fuel solenoid can be fixed. A seized injection pump costs much more.
If you take care of it, a 3TNM68 can run for thousands of hours. If you need one, let Yutian Machinery help you find the right engine for your machine.
Yutian Machinery – Your Partner in Small Diesel Power.
