When Cummins introduced its QSB6.7, the manufacturer used an interesting term to describe the engine—“improved sociability.” It’s easier than saying the engine doesn’t smoke as much or create as much operating noise as the model it’s replacing, the respected QSB5.9. The new model is offered in output ratings from 380 to 480 hp. In testing in a 44-foot express cruiser with pods, a pair of 480-hp QSB6.7s pushed the boat to better than 17 knots in 8 seconds, according to Cummins. The engine’s fuel system is calibrated to deliver optimum fuel economy at cruising speeds. The QSB6.7 meets Tier III standards, and has power-steering and hydraulic pumps that are gear-driven, which improves reliability over belt-driven systems.