Getting more out of thin air
By Charles Plueddeman
An internal combustion engine is little more than a self-igniting air pump. And the more you pump into it, the more power it makes. By pushing a lot more air through its largest four-cylinder cower-head, Suzuki has squeezed 140 hp from an engine that originally made 115.
The DF140 is based on the four-cylinder, 1950cc powerhead introduced last season as the DF115. To boost output by 22 percent
without swelling the engine's size or weight, Suzuki enlarged the cylinder bore from 3.3" to 3.4" yet maintained the 3.5" stroke, thus
increasing displacement by 5 percent to 2044cc. A new camshaft with more lift and duration allows more air to enter the
cylinder. To route that air to the powerhead, Suzuki designed a new intake system that starts with a larger, aft-facing air well located high on the back of the cowl. Finally, top rpm was increased from 6000 to 6200, and the fuel injection computer was recalibrated to increase the fuel supply to match the extra air flow.
The result is a compact outboard that makes 69 hp per liter and weighs just 421 pounds. For comparison, consider the four-cylinder Honda BF130 four-strike that makes 58 hp per liter and weighs 505 pounds. The DF140 even outguns the two-stroke V-6 Mercury Optimax 135, which makes 61 hp per liter, and weighs 443 pounds. The minimal weight and narrow profile of the DF140 make it ideal for light skiffs and dual installations on smaller cats and fishing boats where a pair of 150-hp V-6 outboards might be too much motor and use too much fuel.
Another notable highlight is the DF140's offset driveline, which positions the powerhead forward of the drive shaft and mates the crankshaft to the drive shaft through a gearset. This makes the motor smaller and positions its mass closer to the transom. It also permits gear reduction without a large gearcase. There's a 1.24:1 reduction between the drives and crankshafts and 1.61:1 in the lower unit gearcase, for a total reduction of 2.85:1. A 2.0:1 ratio is more typical in this size outboard. This "low" gear ratio allows the engine to turn a big 14" diameter prop with up to 26" of pitch without bogging, while delivering outstanding acceleration, top speed, and economy. That this performance is four-stroke smooth and quiet is frosting on the cake.
Outstanding power-to-weight ratio for a low-emissions outboard. Quiet, fuel efficient, and bristling with technology. Low gear ratio permits effective use of bigger props. Three Star emissions rating and a standard three-year warranty.
Suzuki has only a limited selection of propellers.
Low-emissions alternatives include the Honda BF130 ($11,195), another fuel-injected four-stroke that's larger and heavier
than the DF140 and lacks its bottom-end punch. The two-stroke Mercury Optimax 135 ($10,606) is a 2.5-liter V-6 that's also larger and more than 20 pounds heavier than the DF140. It's about equal to the DF140 in terms of performance but is louder. Mercury offers the widest range of prop choices in the industry.
Motor Corp., Dept. 8
325 E. Imperial Hwy.
Brea, CA 92822