Suzuki DF140

Suzuki's DF140 is the lightest four-stroke in the 130–140hp range, and despite not having variable valve timing or even the variable air induction of its Honda BF135 competition, I reckon it outperforms all the four-strokes in this power range that I've tested, particularly above 4000 revs. The holeshot acceleration is outstanding for a 2.0lt engine and low noise levels, even at Wide Open Throttle, make it a much more pleasant engine to operate.

As with the DF115, the DF140 has a two-stage gear reduction achieved by having an offset driveshaft with a reduction from the crankshaft and a further reduction in the gearcase. This results in the deepest overall gear reduction in its power range without resorting to a bigger gearcase torpedo diameter which would increase hydrodynamic drag. The DF140 also has the same self-adjusting camshaft drive chain but to handle the 22 per cent greater output from only five per cent bigger piston displacement a water-cooled engine oil cooler is fitted. Like the DF115, the DF140 meets EU2005 and CARB 2008 noise and exhaust emission requirements and has a three-year warranty for recreational usage.

However, because of its relatively small piston displacement the DF140 needs careful propping to achieve its full potential and under normal operating loads it should reach around 6000 revs at WOT. But unlike some of its competition, it returns excellent performance with Suzuki alloy props, dramatically reducing the prop replacement price and saving the clutch dogs from damage when fishing snag-infested waterways.

Another advantage of the DF140 over some of its competition is its light weight - 15 per cent less than another leading brand - which makes a big difference on smaller hulls.

Mounted on a 5.5m Southern Star SF550WR Classic, spinning a 19in alloy Suzuki prop and pushing a total of 1350kg including four adults, the DF140 trolled us at 4.5kmh on 700rpm using 1.5lt/h. Increasing the revs to 2000 returned an average of 10.2kmh using 6.8lt/h and a clean plane was achieved at 27.9kmh on 3400rpm using 17.4lt/h. Due to the electronic management system, which maintains revs as load increases, the DF140 kept us planing across and into 50cm high waves at these revs.

Cruising quietly at an economical 4000rpm, it averaged 41.9kmh and 20.9lt/h, and through full lock figure-eight turns no prop ventilation occurred. At my recommended maximum cruising revs of 5000 the averages were 55.1kmh and 34.4lt/h and into the waves and headwind the Suzy maintained these revs without touching the throttle lever. The alloy prop refused to let go even with some out-trim on the leg. WOT average was 68.1kmh using 52.4lt/h.

Apart from some vibration at 3000 revs coming onto the plane, the Suzuki had very low vibration levels across the rest of the rev range. It was a surprisingly smooth motor.

The DF140 started instantly hot or cold with no oil smoke at any time and warmed quickly from cold. The single lever Suzuki remote control box provided a progressive action into ahead or astern with barely a clunk and, providing the antiventilation plate was kept at least three-quarters immersed, power astern was good and no cooling water starvation occurred.

Powerhead access is good although there are two separate ignition coils for the four spark plugs instead of the integrated coil and spark plug caps of the DF40/50 and V6 Suzies. The engine oil dipstick, spark plugs and water-cooled fuel rail are easily reached and the recommended servicing interval is 50 hours after the first 20 with waterpump impeller replacement required every 100 hours.