NEW TECH

The en­gine builder launches 350hp out­board with dual pro­pel­lers

Motorboat & Yachting - - Contents - Con­tact www.glob­al­suzuki.com/ma­rine

Suzuki’s new 350hp out­board goes un­der the mi­cro­scope plus, Lowrance HDS-16 Car­bon; Dinghy Rings; Yamaha F2.5 out­board; Gill 7014 Black­wa­ter Level Sen­sor; Es­thec lu­mi­nous deck­ing

Suzuki has un­veiled its most pow­er­ful out­board ever – a 350hp V6 4-stroke with some very unique fea­tures. Only two other main­stream en­gine man­u­fac­tur­ers, Mer­cury and Yamaha, can match this power out­put and nei­ther of them can of­fer the Suzuki’s dual-prop setup.

In fact, ev­ery­thing about this new en­gine has been de­signed to of­fer a dif­fer­ent boat­ing ex­pe­ri­ence to its key ri­vals. That starts with the way it has gone about cre­at­ing the ex­tra grunt; rather than re­ly­ing on a su­per­charger (Mer­cury) or a larger-ca­pac­ity en­gine block (Yamaha), it has taken the al­to­gether trick­ier route of squeez­ing more power out of its ex­ist­ing 4.4-litre nat­u­rally as­pi­rated V6. The pay­off is a light, com­pact en­gine with plenty of power, rapid throt­tle re­sponse and low fuel con­sump­tion.

The most sig­nif­i­cant en­hance­ment is an un­usu­ally high com­pres­sion ra­tio of 12.0:1 – the high­est ever for a pro­duc­tion out­board en­gine. This en­ables it to de­velop more power from the same size block with­out the need for forced in­duc­tion from ei­ther a me­chan­i­cally driven su­per­charger or an ex­haust driven tur­bocharger, both of which add weight, sap power and in­crease fuel con­sump­tion. The dif­fi­culty with high com­pres­sion ra­tios is en­sur­ing the en­gine still runs smoothly and re­li­ably with­out the en­gine knock that of­ten af­flicts this type of highly tuned mo­tor. Suzuki claims to have resolved this through a com­bi­na­tion of cool air in­take, twin fuel in­jec­tors per cylin­der and a spe­cial hard­en­ing and fin­ish­ing process for the pis­tons and con­rods.

One of the key in­no­va­tions is a new dual-lou­vre sys­tem that feeds air into the cylin­ders. These spe­cially shaped air in­takes, com­pris­ing two rows of fin-like lou­vres, not only fil­ter out ev­ery last drop of wa­ter and mois­ture be­fore it en­ters the com­bus­tion cham­ber but also helps to cool the air as it passes. Suzuki claims the av­er­age in­take air tem­per­a­tures are 10° cooler than am­bi­ent, sup­ply­ing the com­bus­tion cham­ber with cooler, denser air for a more pow­er­ful com­bus­tion cy­cle. In ef­fect, this acts as a mild form of forced air in­duc­tion.

The use of two fuel in­jec­tors per cylin­der also helps to re­duce knock­ing by en­sur­ing a greater den­sity of atom­ised fuel is in­jected into the cen­tre of the com­bus­tion cham­ber rather than around the edges, as is the case with the cone-shaped spray from a sin­gle in­jec­tor. This re­duces the amount of off-cen­tre com­bus­tion, one of the causes of knock­ing. Be­cause the same amount of fuel can be in­jected faster, it also aids cool­ing, de­liv­er­ing an ad­di­tional 3% power boost.

The sur­face of the pis­tons have been treated with a shot-peen­ing process that leaves mi­cro­scopic dim­ples on the pis­ton face. These help dis­trib­ute the high pres­sures cre­ated dur­ing com­bus­tion more evenly for re­duced wear and a more con­sis­tent power stroke. The con­nect­ing rods and other mov­ing parts have also been strength­ened to cope with the in­creased loads.

TWO PROPS BET­TER THAN ONE

Putting this much power into the wa­ter is al­ways go­ing to be a chal­lenge from the point of view of both grip and me­chan­i­cal strength. A sin­gle pro­pel­ler typ­i­cally uses three big blades to trans­mit power into the wa­ter, while the gears need to be strong enough to with­stand the torque of the en­gine as the blades come up to speed. This in turn re­quires a larger gearcase which gen­er­ates in­creased drag through the wa­ter. Suzuki’s an­swer is to adopt twin con­tra-ro­tat­ing pro­pel­lers that use six smaller blades to give bet­ter ac­cel­er­a­tion while si­mul­ta­ne­ously re­duc­ing the load­ing and size of the gears. This has al­lowed it to de­sign a sleeker leg with­out the torque steer associated with a pow­er­ful sin­gle en­gine spin­ning a big prop in one di­rec­tion only. It claims this is par­tic­u­larly no­tice­able on larger boats car­ry­ing heavy loads of fuel and peo­ple.

Last but not least, the new en­gine tips the scales at a rel­a­tively mod­est 330kg (mid­way be­tween the 346kg Yamaha F350 and the 303kg Mer­cury Ver­ado 350), while the slen­der de­sign of its nar­row-an­gle V6 en­gine makes it eas­ier to fit mul­ti­ple in­stal­la­tions on tran­soms with lim­ited space. Suzuki’s usual lean burn tech­nol­ogy and elec­tronic throt­tle con­trol should en­sure im­pres­sive fuel econ­omy and easy han­dling for such a pow­er­ful unit, although no com­par­isons with ri­vals are cur­rently avail­able.

The new en­gine will be launched at the Southamp­ton Boat Show in Septem­ber with the first de­liv­er­ies ex­pected in De­cem­ber. Pric­ing will be an­nounced at the show.

KEEP­ING A COOL HEAD

The slen­der de­sign of the cowl­ing is well suited for mul­ti­ple en­gine ap­pli­ca­tions

MY TAKE I’m in­trigued to see how well this en­gine works. I like the fact that it doesn’t rely on forced in­duc­tion to gen­er­ate more power, but will it match the low-rev torque of the Yamaha and Mer­cury? Hugo

NAV­I­GA­TION Mel Bartlett

Nick Burn­ham PROD­UCTS

Com­pact gear sets al­low for a slim­mer cas­ing for re­duced hy­dro­dy­namic drag

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