New
Yanmar53 HP
Yanmar 4JH45E 53.8HP
diesel
$4,050.00
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New
Yanmar
Yanmar 3YM20 21HP
$2,170.00
The Yanmar 3YM20 is a compact and fuel-efficient 21HP marine diesel engine designed for sailboats and small motor vessels. It offers quiet operation, low vibration, and proven Yanmar reliability.
Horsepower
21 HP
Fuel Type
diesel
Displacement
0.854 L / 52.1 cu. in
Stroke
4-stroke
Rated Output
15.3 kW / 21 mhp
Rated Speed
3600 rpm
In Stock (3 available)
Free shipping on orders over $500
90-day warranty included
Description
The Yanmar 3YM20 is a naturally aspirated, three-cylinder, 4-stroke diesel engine built for dependable inboard marine use. Its lightweight design and simple mechanical fuel injection make it easy to maintain while delivering excellent fuel economy and long service life. Ideal for sailboats, cruisers, and auxiliary propulsion, the 3YM20 is widely used for both new installations and repowering projects.
Specifications
SKUY451076
BrandYanmar
CategoryInboard Engines
ConditionNew
Horsepower21 HP
Fuel Typediesel
Displacement0.854 L / 52.1 cu. in
No. of Cylinders3 cylinders
Stroke4-stroke
Weight243.00 lbs
Rated Output15.3 kW / 21 mhp
Rated Speed3600 rpm
Cylinder Bore x Stroke70 mm x 74 mm / 2.76 in x 2.91 in
Combustion SystemIndirect Injection, In-line Pump
AspirationNatural
Alternator12V - 125A
Dry Weight110 kg / 243 lbs
Dimensions694 mm x 463 mm x 600 mm
ControlsMechanical
CertificationsRCD 2 EPA Tier 3 EPA Tier 3C BSO II EMC
Frequently Asked Questions
What is the Yanmar 3YM20 engine?
The Yanmar 3YM20 is a 3-cylinder, 4-stroke, vertical water-cooled marine diesel engine producing approximately 21 metric horsepower (15.3 kW) at 3600 rpm. It is designed for use as an inboard propulsion engine on small sailboats and recreational vessels.
What are the key technical specifications?
Power Output: ~21 HP (15.3 kW) at 3600 rpm Displacement: 0.854 L (854 cc) Cylinders: 3 inline Combustion System: Indirect injection, in-line pump Aspiration: Naturally aspirated Cooling: Fresh water cooling with heat exchanger Alternator: 12 V – 125 A Dry Weight: ~110 kg (243 lbs) (without gear) Controls: Mechanical
What type of cooling system does it use?
It uses a fresh water cooling system with a heat exchanger, which helps protect the engine from saltwater corrosion and maintains proper operating temperatures.
What types of boats is the 3YM20 suited for?
This engine is ideal for small sailboats, cruisers, tenders, and light recreational motorboats where reliable diesel propulsion and fuel economy are required.
What is included in the standard engine package?
Exhaust mixing elbow (L-type) Alternator (12 V – 125 A) B20 control panel Flexible engine mounts Expansion tank for freshwater cooling Electric stop solenoid Belt safety cover
Are there optional accessories available?
High-riser mixing elbow Extension wiring harness (4 m or 6 m) Dual harness for a second control station TFX sidemount control head Hot water kit Saildrive leg extension Spare parts kit.
What is the fuel system like?
The engine uses indirect injection with an in-line pump. This is a simple but robust diesel fuel system well-suited to marine use.
How often should I perform routine maintenance?
Routine maintenance such as checking engine oil, coolant, belts, and filters should be performed regularly — generally every 100 engine hours or at least annually. Refer to the official Yanmar operation manual for detailed intervals.
Can I do maintenance myself?
Basic checks (oil level, coolant level, belts) can be done by owners experienced with marine engines. However, major services and diagnostics should be done by an authorized technician to ensure proper operation and warranty support.
What type of fuel and oil should I use?
Use marine diesel fuel that meets local specifications. For oil, follow the recommendations in the Yanmar manual — typically a quality diesel engine oil meeting API and SAE standards suitable for marine diesels.
Is this engine reliable?
Yanmar’s YM series engines are known for durability, smooth performance, and fuel efficiency when properly maintained, making them a trusted choice in small marine propulsion.
