Suzuki DF140A four-stroke outboard launch, Brisbane

How do you improve upon the best-selling engine in your range without alienating the very commercial and recreational customers who got it to that lofty position in the first place, particularly if most of them reckon there’s nothing wrong with the current donk in the first place? What if that engine holds a unique market all to itself and has pretty much kept its competitors at bay for almost a decade? 

These questions must have caused countless sleepless nights for the development team charged with rejuvenating Suzuki’s ground-breaking DF140, and one would suspect mass hara-kiri would ensue should they miss the mark.

Often when we conduct comparison tests we’re presented with two or more similar packages to review. We take it for granted that weights and fit-ups are identical, and, to be fair, that’s normally the case. However, the Haines Group, true to its word, was adamant that in this instance both new and old engines were tested on an identical platform — a new Signature 543F… also the same Signature 543F. So after we’d all completed our initial run with a sweet but well used DF140 (with 728 hours on the clock), they trailered the boat to Cleveland’s Bayside Suzuki Marine with the assembly in tow. To further alleviate any suggestion of skulduggery, the Suzuki crew turned off the smoke machine, wheeled away the mirrors and treated us to a ring-side seat as the 543F underwent a heart transplant to the new lightweight Lean Burn DF140A. We adjourned to the local Grand View Hotel for the mandatory briefing and upon our return to Raby Bay boat ramp, the rejuvenated 543F, now sporting the edgy new DF140A, was waiting for another spanking. As we powered away from the boat ramp in atrocious conditions, we were left in no doubt that that the fettling and retooling of 168 new parts was immediately apparent. Less obvious was the resulting weight saving of 7kg, although picking up both cowls revealed a weight reduction of almost 50 per cent for the new one.

POINTS OF DIFFERENCE

So what does this all mean and are the improvements going to be appreciated by the end users? I’d have to yell a resounding, “Yes”. Starting was quicker courtesy of “Smart Start – One Touch Starting” and vibration levels at low revs were noticeably lower than those of the previous 140. The adjustable Electronic Trim Limiter, which can be pre-set by the operator, is a sure-fire winner. Lean Burn, which was introduced recently to the DF250AP and DF300AP, allows the engine to run a richer air / fuel ratio resulting in fuel savings of up to 14 per cent depending upon conditions. Two-stage reduction gearing delivers more grunt out of the hole while swinging a larger prop. The new 140A is also now NMEA enabled, allowing it to be digitally interfaced with multifunction gauges such as the installed Garmin GMI 10s and networked with NMEA-compatible sounder and GPS units. Suzuki refers to it as its Interface Linkage System. And then there’s Troll Mode, which is a must-have if towing plastic and metal is your bag. At a paltry $135 plus installation it’s a steal, allowing you to set and adjust your trolling speed in 50 rev increments.

But wait, there’s more! The new DF140A now forms the basis of the new DF115A and DF100A, which is great news for those who require the torque, without the top end. The low weight (179kg in longshaft form) and compact proportions of this series would also make them ideal for twin engine installations on many larger trailerboats. And for the masochists out there, the DF100A and DF115A engines are also available with the optional Multi Function Tiller Handle, for those who prefer to steer from the rear.

Performance wise, there is a distinct kick in the mid-range and the engine felt and sounded remarkably smooth throughout the rev range from 500rpm through to a heady 6300rpm. Outright speed and revs were almost identical, but the new kid on the block felt more willing and responsive, despite its meagre four engine hours. The original DF140 exhibited an obvious resonance between 2000rpm and 3000rpm, but seemed far less conspicuous with the new one. Suzuki has also massaged the engine note, which is now throatier yet never intrusive. Overall Suzuki has managed to take a great engine and make it even more entertaining; I’m now champing at the bit to score a test of the Signature 543F in full-blooded fishing mode.

So it seems the Suzuki techs are safe this month and they can sheath the silverware. They’ve nipped, tucked and augmented the DF140 in all the right places and the final result is a special thing indeed.