Suzuki DF115

The Suzuki DF115 is the first 115hp outboard in the world to comply with the EU 2004 exhaust emission regulations, scheduled to come into effect in January 2005. These regulations are tougher than CARB (California Air Resources Board) 2008 requirements.

Yet unlike some automotive engines that have lost significant power and torque outputs to comply with increasingly tough European Union emission laws, the automotive-based DF115 appears to be none the worse for reaching the EU 2004 standards for clean running. It accelerates crisply across its entire rev range and provides DFI-like throttle response from 4000rpm to wide open throttle, yet is substantially more fuel efficient (and quieter) in the 2000-4000rpm range used most frequently by offshore anglers.

Although the DF115 develops 24.6hp less than its DF140 counterpart (see Trailer Boat October 2002), it has only 94cc less piston displacement and still has the two-stage gear reduction system that allows for a deeper, more thrust-efficient gear ratio without increasing gearcase torpedo diameter. A usefully large output alternator produces 15amps more than the Mariner/Mercury F115 and Yamaha F115A.

Yet for all of these engineering features and a 209cc greater piston displacement than the F115 and F115A, the DF115 weighs only 4kg more than the Yamaha F115A and 5kg less than the Mercury F115. And both the F115 and F115A have belt-driven camshafts that need replacing about every 800 hours, whereas the DF115's camshaft chain drives are designed to last the life of the engine.

Until Tohatsu releases its TLDI 115 and Mercury Marine gets stocks of its Optimax 115 out into the marketplace, the Bombardier Ficht 115 is currently the only DFI two-stroke in this power range. It weighs 160kg, so it's substantially lighter than any of the four-strokes. But as the DF115 appears to provide better acceleration across the rev range than the other four-strokes tested on similar hulls, how does the sequential multi-point EFI of the DF115 compare with the single fuel DFI of the Ficht 115 for performance and fuel efficiency?

Of course the different test hulls provided did affect the performance and fuel efficiency of the motors I tested, so the following comparison should be taken as a guide only.

Mounted on a Clark 5.7 centre-console, the demo DF115 returned stunning performance, even by DFI two-stroke standards. It started instantly hot or cold with no oil smoke appearing at any time using Suzuki SAE10W40 oil and had lower vibration levels than the Ficht in my view. Providing the anti-ventilation plate was kept at least three-quarters immersed, power astern was good and no cooling water starvation occurred.

Spinning a 17in-pitch stainless steel prop and pushing a total of 1100kg including four adults, the DF115 trolled at 6.9kmh on 700rpm using 1.2lt/hr. In comparison, on a Quintrex 530 Freedom Sport, spinning a 17in stainless steel prop and pushing a total displacement of one tonne, a Bombardier Ficht 115 used 1.0lt/hr at 650rpm and averaging 4.4kmh. Unusually for a four-stroke, the Suzy returned 30 per cent better fuel efficiency.

At offshore trolling speeds at 2000rpm, the Clark averaged 12.8km/h and the Suzy 5.0lt/hr compared to 13.5 and 7.0 for the Ficht. The Suzy returned 33 per cent better fuel efficiency.

Due mainly to its ability to trim-in well past perpendicular with the water, the DF115 planed the Clark cleanly at only 20.3km/h on 3000rpm compared to 23.5 and 2800 for the Ficht. Cruising quietly at 4000rpm, the DF115 returned an average of 40.0km/h using 16.5lt/hr whereas the Ficht averaged 44.7km/h and 21lt/hr, enabling the Suzy to return 14 per cent better fuel efficiency.

Through tight figure-eight turns at 4000rpm there was no prop ventilation with either motor despite both hulls having deep full length keels.

At WOT the DF115 averaged 57.9km/h on 5750rpm using 39.0lt/hr compared to 64.9km/h on 5550rpm using 45.0lt/hr with the Suzuki returning three per cent better fuel efficiency, although at 11 per cent slower speed. At these revs the Suzy was significantly quieter than the Ficht.

Access to the powerhead is good with the oil dipstick easily reached. Recommended servicing intervals are every 50 hours or six months after the first 20 hours, and the waterpump impeller should be replaced every 100 hours or once a year. The oil sump has sufficient capacity to effectively reduce oil sludging between oil/filter changes. For recreational applications the warranty provides three years of general coverage.