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  • Yanmar 12AYM-WGT; The High Speed Marine Engine that Makes 1,822 hp and 6,300 lb-ft of Torque

Yanmar 12AYM-WGT; The High Speed Marine Engine that Makes 1,822 hp and 6,300 lb-ft of Torque

High-Speed, Eco-Efficiency and 6,300 lb-ft of Torque for Hard-Working Marine Vessels

John Lehenbauer
May 26, 2016
Photographers: Courtesy of the Manufacturer
Yanmar is a manufacturer of high-speed commercial marine diesel engines, and the 12AYM-WGT is its largest, highest-output powerplant for seagoing vessels. With 1,822 hp and 6,300 lb-ft of torque, this workhorse provides ample power for ships to carry out their required duties, and still maintain stable cruising speeds under load. The abundance of low-rpm torque, thanks to the use of a long piston stroke, makes the 12AYM-WGT very well suited for use in tugboat applications, where large amounts of grunt are needed.
This engine is designed to be tough and reliable, and it will provide economical, clean power (it meets 2016’s emission standards). Yanmar is able to do this with a development that it calls EcoDiesel Technology, which does not use any electronic engine controls to govern emissions. The management is done mechanically, to avoid failures caused by electronics’ exposure to engine-compartment heat. The EcoDiesel technology concentrates on the engine’s combustion process. Improvements of the combustion conditions in the cylinder lead to a reduction in fuel consumption, smoke and NOx emissions. Normally, when trying to reduce NOx, fuel usage and exhaust output are negatively affected. But, the Eco Diesel’s more efficient combustion comes from the use of fuel injectors with multiple micro-sized holes, deeper combustion chambers and reshaped 4–valve-per-cylinder heads. This new efficiency also provides the engine with increased service intervals as well as horsepower and torque gains.
Photo 2/4   |   001 Yanmar 12AYM WGT Marine Engine
The 12AYM-WGT is Yanmar’s largest high-speed commercial marine engine. Its 1,800 hp and 6,300 lb-ft allow working ships to operate quickly, economically and in compliance with emission standards.

A boost compensator, which regulates the air/fuel mixture in each cylinder, helps reduce black smoke and fuel consumption under hard acceleration. An internal EGR system is used to further lower emissions. The EGR is controlled by the lift of intake and exhaust valves, which eliminates the need for external control devices. The engine’s design provides a fuel economy gain of 53 gallons of fuel per hour over older models, and allows the 12AYM-WGT to meet Tier II emissions standards. The engine is expected to meet Tier III standards by 2017.
Engines that are used in marine settings need to be durable and serviceable. Yanmar addresses durability in a couple of ways. Sillicard, an artificial ceramic made from silicon carbide that’s second only to diamonds in hardness, coats the surface of the cylinder liners to make them tough and resistant to wear. The liners are then paired with ductile cast-iron pistons that use a nitride stainless steel ring with very tight tolerances.
The engine uses two heavy-duty injection pumps instead of one to improve serviceability in the fuel system. This allows for each bank of injectors on the V-12 to have its own pump (the pumps are sourced from Yanmar’s marine six-cylinder engines).
The engine block has large inspection windows on the side of the casting, which allows ease of piston replacement. Another innovative design used on the 12AYM-WGT is the use of individual heads for each cylinder. The unique configuration facilitates easier repairs.
Photo 3/4   |   002 Yanmar 12AYM WGT Marine Engine
The twin turbochargers and air-to-water intercooler are mounted on the rear of the engine so exhaust can be easily routed out of the vessel.

Building marine diesels is nothing new for Yanmar. The company built its first engine over 90 years ago. That powerplant had low compression and burned fuel oil, which doesn’t support much horsepower, instead of diesel. However, by continuing to innovate, Yanmar has become the maker of very efficient, high-powered marine-diesel engines
Engine: Yanmar 12AYM-WGT
Displacement: 40.8L (2,489ci)
Engine Layout: V-12, 90 degree
Valvetrain: DOHC
Bore x Stroke: 6.10 x 7.09 inches (155 x 180mm)
Compression Ratio: 13.2:1
Head material: Iron
Block material: Cast iron
Piston material: Ductile Cast-iron
Power: 1,822 hp @ 1,940 rpm
Torque: 6,300 lb-ft @ 1,350 rpm
Induction: Twin turbocharged
Exhaust: Water-cooled, cast-iron manifolds
Intercooler: Air-to-water
Cooling System: Seawater and freshwater/coolant
Coolant Capacity: 59.4 gallons
Fuel System: Direct injection
Lubrication System: Wet sump
Lubrication capacity: 45 gallons
Dry Weight: 10,736 pounds
Length: 103 inches
Width: 65 inches
Height: 67 inches
Photo 4/4   |   003 Yanmar 12AYM WGT Marine Engine