Suzuki's DF40 and DF50 four-strokes

Suzuki has managed what many pundits thought impossible. The first outboard engine maker to introduce electronic multi-point digital sequential fuel-injection has produced the new award-winning DF40 and DF50 four-stroke outboards which deliver environmental-friendliness and snappy performance.

With its DF40 and DF50, Suzuki has taken out the prestigious International Marine Trade Exhibit and Conference (IMTEC) award in America. That is, for the second year running, which is also a world first. Not surprisingly, the Japanese engine maker has declared that high-tech four-stroke engines are the way of the future. Suzuki has both restructured and reduced its 1999 outboard range to concentrate on its whiz-bang four-strokes.

This move fuels the argument that traditional two-strokes have reached their used-by date, even though Suzuki will continue to supply markets such as Australia which are not constrained by tough marine emission laws as yet.

For the release of the new 40/50 hp models in Sydney last month, Suzuki fitted up a range of trailerable aluminium boats. It also had Rugby League star Andrew Ettingshausen on hand to take delivery of his new Suzuki-powered Renegade centre-console not that football stars were needed, mind you.

Of all the four-stroke outboards I have sampled, I found Suzuki's models the most impressive for power. With a higher rev range of up to 6500rpm, instead of the usual 5500rpm we are accustomed with in the case of two-strokes, the stylish outboards deliver instant acceleration and the kind of throttle-response Australian boaties are used to.

The fuel-injection Suzuki outboard showed none of the bottom-end lag that can see some boats struggle to get onto the plane. Instead, as you leaned on the throttle, the Renegade boats jumped straight out of the water.

Suzuki's new four-strokes are perfect motors for fishing and fun-running boats, and the new DF40 and DF50 have both been developed from three-cylinder car engines.

On the technical side, they have dual overhead cams with four-valves-per-cylinder, direct ignition, a tuned long-branch intake manifold, and another first, an oil-bathed timing chain with an automatic hydraulic tensioner.

Suzuki claims this latter feature gives greater reliability and durability. It attributes its trick fuel-injection system with lower consumption, smoother starting, stable idling and outstanding throttle response.

Like the high-tech DF60 and DF70 which won the IMTEC award in 1997, Suzuki's new DF40 and DF50 come with computer brains. Their Engine Control Module provides ideal fuel supply in any environment. This contributes to extended sparkplug life, which need changing only after the first 200 hours. Other features include idle-air control, a fast-idle function, and low-speed safety check mode.

With a larger cylinder bore and longer stroke than automotive motors, the DF40 and DF50 have also been beefed up with strengthened cylinder heads, blocks, crankshafts, camshafts and pistons.

According to field reports made available to Suzuki, the local water police are getting twice the life from four-stroke motors, and the National Park and Waterways authorities are embracing the new breed, too.

Fuel economy is important in such applications. Indeed, Suzuki says its new powerplants deliver a saving of at least 30% in fuel compared with the same horsepower two-stroke.

Coupled with a multi-function tachometer which alerts you to service requirements, which are every 100 hours after the first 20-hour service, and the new DF40 and DF50 are indeed impressive bits of engineering.

But just as impressive is the fact that Suzuki recognises the importance of propellers when it comes to four-stroke powerboating. It makes all its own stainless props in a range that can cover just about any boating situation. Typically, the DF40 and DF50 will be fitted with 13, 14 or 15-inch pitch propellers.

"Our product technology is now ahead of its competition, as evidenced by back-to-back IMTEC awards, and by the fact that the all-new four-stroke engines already pass the 2006 Environmental Protection Agency emission regulations [applying in Europe and America]," says Graeme West, Suzuki's national marine manager.

"Technology for technology's sake is of no benefit, but technology that delivers a better performing and cleaner product is certainly something worthwhile... we have achieved our goal," he adds.

Presently, Suzuki manufactures four-stroke outboards from 9.9-70 hp. Its new DF40 and DF50 weigh 108 kg in long-shaft (20in) form. The DF40 has a full-throttle operating range of 5200-5800rpm and the DF50, 5900-6500rpm.

Both motors come with three-year warranties. Recommended retail prices are $9,450 for the DF40 and $9,900 for the DF50. For more information, contact your Suzuki dealer or Suzuki Australia, tel (03) 9931 0500.