SALE! Yanmar 3YM20 Marine Diesel Engine 21HP – USED

The Yanmar 3YM20 is really a scaled-down version of the beautiful Yanmar 3YM30 diesel engine, which from owner reports has the same running qualities of low vibration and exhaust smoke emissions. It’s one of the few small Yanmar diesel engines.

The indirect injection Yanmar 3YM20 displaces 854cc and has a simple OHV design with pushrods operating the two valves-per-cylinder and a slightly under-square bore:stroke ratio for better combustion efficiency. It develops a maximum of 21.7bhp at 3600rpm at 250C fuel temperature or 20.5bhp at 400C. The maximum continuous output is 19.7bhp at 3490rpm and the engine is rated to 250 hours of running per year, with no more than 10 per cent of this at Wide Open Throttle.

The maximum torque on the Yanmar 3YM20 boat engine is an impressive 50.5Nm at 2200 to 2500rpm, with plenty of torque still above and below this range.

To meet EU and US exhaust emission laws, the 3YM20 has heat exchanger cooling with hot water take-off and centrifugal freshwater cooling pump and a gear-driven saltwater pump.

The voltage regulated alternator pumps out up to 60amps and can be upgraded to an 80amp unit. Both the alternator and starter motor are mounted high on the engine, away from bilge water, though this should not be there in a ’glass hull. And you don’t want it either, as only electric starting is fitted!

The main drawback is that a down-angle gearbox is not available, so care has to be taken when mounting the engine to avoid oil starvation when the hull is pitching underway. But, cleverly, Yanmar offers two boxes that have a taller ahead gear than astern, allowing the engine to reach its torque band faster when going astern in a marina. These boxes have either 2.21:1 or 2.62:1 reductions ahead and 3.06:1 astern and mechanical cone clutches for reliability and servicing ease.

Complete with box, the 3YM20 measures 694mm long by 463mm wide and 600mm high, so it is a fairly tall engine, compounded by the forward end being raised as there’s no down-angle box. This model weighs 130.3kg dry.

An SD20 saildrive model is also available with 2.64:1 reductions ahead and astern and weighs 150kg dry. The SD20 has a long-running double seal design with water ingress alarm between the seals – just as well as the hull opening for a saildrive is way bigger than the hole for a shaftdrive!

Yanmar recommends using good quality mineral-based SAE 10W30 or 15W40 oil depending on the anticipated ambient temperature range between oil and filter changes. For infrequently used engines, recommend doing this every six months.

Specifications

Rated Output: 15.3 kW / 21 mhp

Rated Speed: 3600 rpm

Displacement: 0.854 L / 52.1 cu. in

No. of cylinders: 3 cylinders

Cylinder Bore x Stroke: 70 mm x 74 mm / 2.76 in x 2.91 in

Combustion system: Indirect Injection, In-line Pump

Aspiration: Natural

Alternator: 12V - 125A

Dry weight without gear: 110 kg / 243 lbs

Dimensions: 694 mm x 463 mm x 600 mm

Controls: Mechanical

Certifications: RCD 2 EPA Tier 3 EPA Tier 3C BSO II EMC

NOTE:

1 kW = 1.3596 mhp = 1.34102 bhp

Fuel condition: density at 15°C = 0.842 g/cm³

Technical data is according to (ISO 8665) / (ISO 3046)

Fuel temperature 40°C at the inlet of the fuel injection pump (ISO 8665)

Length includes KM2P-1 marine gear & height includes U-type elbow

(Dimensions may vary with other gears/elbow)

Standard Engine Package

Exhaust mixing elbow [L-type]

Alternator 12V – 125A

B20 panel

Flexible mounts

Expansion tank for fresh water cooling system

Electric stop solenoid

Belt safety cover

Optional Accessories

High-riser mixing elbow [instead of L-elbow]

Extension wire harness [4m, 6m]

Dual harness [for 2nd station]

TFX Sidemount control head

Hot water kit with cocks

Extension saildrive leg [50 mm]

Propeller cone nut kit SD25

On-board spare parts kit

• Availability: In Stock
• Model: 3YM20
• Brand: