The age-old argument among mariners concerning twin-engine versus single-screw boats has taken a new twist. Recent results comparing a single-engine Yanmar 6LP-series diesel sterndrive to twin gas outboards gave the diesel engine advantages in nearly every category. Producing 300 crankshaft hp at 3,800 rpm, the 6-cylinder, 6LP-STZE is one of Yanmar Diesel's most popular engines among boatbuilders. Its light weight and small footprint have made it the choice for many gas-to-diesel and diesel-to-diesel repowering projects as well. Equipped with a Mercruiser Bravo Three sterndrive, the combination weighs only 1,100 pounds and, on a 31-ft. open console fishing boat, burns less than 11 gph at nearly 35 mph. That's over three miles per gallon.