Suzuki’s new 350 out­board sets a high stan­dard.

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More than three years ago, a Suzuki en­gi­neer­ing and de­sign team in Ja­pan set out to cre­ate a 350 hp out­board that would break new ground in fea­tures, per­for­mance and ef­fi­ciency. The team had a watch­word for this project — Geki, Ja­panese for “part­ing the wa­ter.”

This be­came a driv­ing force be­hind an en­deavor to re­think how a big, pow­er­ful out­board should func­tion, and then to strive to bring it to life. Based on my time run­ning the en­gine in sev­eral con­fig­u­ra­tions and get­ting the tech scoop from Suzuki’s en­gi­neer­ing team, I be­lieve that all that cre­ativ­ity, risk and toil paid off.

The new DF350A of­fers a num­ber of in­no­va­tions, in­clud­ing a lower unit un­like that of any other out­board to­day. A pair of con­tra-ro­tat­ing three-blade pro­pel­lers de­liver power to the wa­ter. Of course, the MerCruiser Bravo Three and Volvo Penta DuoProp stern­drives, as well as the now-dis­con­tin­ued VMax TRP 150 out­board from Yamaha, also fea­ture twin props, boast­ing ben­e­fits we have come to ap­pre­ci­ate: strong hole shot, min­i­mal prop torque, bet­ter bite in turns, as well as great han­dling in for­ward or re­verse.

The DF350A of­fers the same ad­van­tages, plus a few more. Con­tra-ro­tat­ing twin props al­low for dis­tri­bu­tion of torque across two smaller gears. This keeps the gear case as small as pos­si­ble to in­crease ef­fi­ciency and boost top speed yet still ac­com­mo­date the torque.

To main­tain a smaller lower unit, Suzuki en­gi­neers moved the shift­ing sys­tem above the gear case. They also re­fined the hy­dro­dy­nam­ics us­ing com­puter sim­u­la­tions to cre­ate a su­per-slip­pery shape and feed clean wa­ter to the props. The new de­sign re­po­si­tions the pri­mary cool­ing wa­ter pickup to the front of the bul­let, with a sec­ondary pickup on the un­der­side, just for­ward of the skeg.

Yamaha boosts out­board horse­power to the 350 range by uti­liz­ing greater

dis­place­ment, as with its 5.3-liter V-8 F350 out­board. Mer­cury boosts the pres­sure of the in­take sys­tem with its su­per­charged 350 Ver­ado. Suzuki took a dif­fer­ent course.

At 4.4 liters, the DF350A’s dis­place­ment is in­deed slightly higher than Suzuki’s DF300AP’s 4 liters. Yet its 12-to-1 com­pres­sion ra­tio — the high­est so far for an out­board — is what makes the dif­fer­ence.

While higher com­pres­sion ra­tio re­sults in greater horse­power per cu­bic inch, it also holds the po­ten­tial to in­duce det­o­na­tion (aka “knock”) that can hurt per­for­mance and dam­age an en­gine.

A key to pre­vent­ing knock is to keep the in­take as cool as pos­si­ble. To do this, the DF350A fea­tures an in­take in the hood that feeds air di­rectly to the en­gine. A se­ries of small lou­vers wick away mois­ture as air ac­cel­er­ates through the slots, so the air is dry and no more than 10 de­grees above the am­bi­ent tem­per­a­ture.

Suzuki also en­gi­neered the DF350A with two fuel in­jec­tors per cylin­der. These not only si­mul­ta­ne­ously de­liver a finely at­om­ized charge of fuel but also cool the in­take air more ef­fec­tively than a sin­gle in­jec­tor.

A num­ber of fea­tures carry over from the DF300A, in­clud­ing elec­tronic throt­tle and shift for smoother con­trol, Lean Burn to max­i­mize fuel ef­fi­ciency, an off­set drive shaft that shifts the cen­ter of grav­ity for­ward, two-gear re­duc­tion to help keep the gear case com­pact, vari­able valve tim­ing for op­ti­mal low- and mid­speed power and ef­fi­ciency, and a self-ad­just­ing tim­ing chain that re­quires no main­te­nance.

Like many other Suzuki out­boards, these en­gines are ex­ceed­ingly quiet, es­pe­cially at idle. But even un­der­way, the em­anated noise is rel­a­tively low. On our runs, the DF350A vaulted out of the hole with head-snap­ping ve­loc­ity and held its bite in tight turns with re­mark­able tenac­ity.

This 350 will find ap­pli­ca­tion on a wide range of boats, but Suzuki is fo­cus­ing much of its at­ten­tion on the grow­ing num­ber of big cen­ter con­soles sport­ing triple and quadru­ple out­boards. A pop­u­lar horse­power in this cat­e­gory, only two other brands — Mer­cury and Yamaha — cur­rently of­fer 350 mod­els.

There’s an­other ad­van­tage here to hav­ing con­tra-ro­tat­ing props: It elim­i­nates the need to mix right- and left-hand ro­tat­ing motors in mul­ti­ple-out­board in­stal­la­tions. With 27-inch cen­ters, the DF350A fits the same tran­som bolt pat­tern as the DF300A, mak­ing for a rel­a­tively sim­ple retro­fit, be it sin­gle or mul­ti­ple out­boards.

XL (25-inch shaft) and XXL (30-inch shaft) mod­els are avail­able, weigh­ing 727 and 747 pounds, re­spec­tively. These are about 35 pounds lighter than the Yamaha F350 but around 60 pounds heav­ier than the Mer­cury 350 Ver­ado. Suzuki of­fers the DF350A in two col­ors: pearl neb­u­lar black and cool white. Pric­ing was un­avail­able at press time. —

SPEED GAIN In com­par­ing test notes on a Dusky 33 Open Fish­er­man, twin Suzuki 350s boosted top speed by 7.1 mph over twin Suzuki 300 out­boards.

TWIN-PROP DRIVE Con­tra-ro­tat­ing props help keep the gear case small and hy­dro­dy­namic.

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