Twin-Crank Diesel Outboard Engine Is a Smooth Operator

Diesels are virtually unheard of in the world of outboard boat engines because of their weight, cost, noise and vibration. But researchers say their unusual twin-crankshaft design addresses all those issues.

An 800-cc demonstration engine was presented during last week's SAE World Congress in Detroit by Germany's Neander Motors AG and FEV North America Inc.

The two-cylinder turbocharged engine produces 55 hp and 86 lb-ft of torque. It weighs 155 kg (342 lbs), which is comparable to a similarly performing gasoline engine.

Each piston has two connecting rods, which drive counter-rotating crankshafts that are geared together. The architecture balances out several orders of vibration, resulting in dramatically smoother operation than a conventional design.

The twin connecting rods also mean virtually no side forces on the pistons, thus reducing internal friction. The design enables a smooth-running engine with fewer pistons, thus reducing mass and cost, according to the company.

Neander says its diesel designs are roughly 35% more efficient than gasoline engines and 10% more efficient that conventional diesels. The company's 1- and 2-cylinder diesels offer a power range between 12 hp and 110 hp.