New marine diesel from Yanmar - Marine Propulsion

Diesel Progress North American Edition, July, 2003

Earlier this year, Yanmar officially unveiled a new diesel that establishes a new top end to its pleasure marine line. The 6SY-STP diesel is an electronically controlled, 12 L engine rated 720 hp. Developed in cooperation with Scania, which produces the base engine, it is engineered to meet the specific requirements of marine pleasure boats and is marketed exclusively by Yanmar.

"The 6SY-STP is just the first in a series of larger Yanmar engines that will complement our successful line of lightweight, powerful diesels," said Tom Calhoun, vice president of Yanmar Diesel, Adairsville, Ga. "We expect to see initial installations of the new engine completed by this fall"

The 6SY-STP engine is an in-line, 24-valve six-cylinder unit with a bore and stroke of 127 mm x 154 mm and an overall displacement of 11.7 L. It incorporates charge-air cooling through a two-stage freshwater cooler that is integral with the heat exchanger.

The heart of the new engine, Yanmar said, is an electronic management system that monitors and processes data such as speed, turbo-charger boost, coolant temperature and throttle setting. The system then adjusts the timing of the electronic injectors and fuel flow to ensure maximum combustion and fuel efficiency in response to operating conditions. Using Communications Area Network (CAN) protocol, the engine is also able to communicate with other monitoring systems.

Other significant features of the 6SY-STP diesel include separate cylinder heads for each cylinder, allowing for easier onboard servicing and a high-efficiency, multiplate oil cooler with internal connections for oil and coolant. Mounted within the engine block, the oil cooler minimizes ex- posed plumbing and pipe work.

The engine block is a cast iron alloy and the connecting rods are constructed of one-piece, press-forged steel alloy Also a steel alloy the crankshaft's bearing surfaces are hardened and polished. With dimensions of 56 in. long x 34 in. wide x 41 in. high, the fully equipped engine weighs in at just under 2560 lb.

With the addition of the 6SY-STP diesel, Yanmar's pleasure marine line now covers a range of 10 hp to 720 hp.

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