Smaller and quieter V-6s were introduced in 1991 in the form of the Evinrude Spitfire and the Johnson Silver-Star series. These outboards featured a new flushing device that could be used to flush the engine with fresh water while it was running. The Spitfire and Silver-Star models also used an infra-red sensor system called Optical Ignition System (OIS 2000). This system automatically advanced the engine timing to eliminate unwanted timing changes. Other advancements in 1991 included smaller, more fuel efficient diesel stern drive models. The OMC Cobra Diesel was a 970-pound, 3.2 liter, six-cylinder monoblock inline powerhouse that produced 205-hp at 4300 rpm.