Power & Tech­nol­ogy

The de­mand for speed has been around since wa­ter’s been wet, but don’t for­get that great per­for­mance is about more than sheer horse­power.

Power & Motor Yacht - - IN THIS ISSUE - By Peter Fred­erik­sen

The de­mand for speed has been around since wa­ter’s been wet, but great per­for­mance is about more than just ponies.

It seems boat own­ers are al­ways chas­ing speed. Skip­pers of sport­fish­er­men want faster craft to get off­shore in a hurry and re­main on the grounds longer with their lines in, par­tic­u­larly dur­ing a high-pro­file tour­na­ment, when mil­lions of dol­lars are on the line. Speed is al­lur­ing for own­ers of other boat types, too. Some peo­ple sim­ply want to drive the fastest boat at a race event. Oth­ers want to set speed records for a par­tic­u­lar yacht style, as John Staluppi did with his 140-foot Mil­len­nium su­pery­acht, The World is Not Enough. (It re­port­edly topped 66 knots more than a decade ago.) But an owner’s de­mand for speed can some­times con­flict with physics, or the pref­er­ences of naval ar­chi­tects and boat builders.

The de­sire for speed will be around for­ever. That much is proven in the surge of new mega-horse­power out­boards. If you want more speed from your out­board-pow­ered boat, just drill more holes in the beefed-up tran­som, add an­other sta­ble of horses and hold onto your hat.

It’s a dif­fer­ent story for diesel en­gines, though, as in­stal­la­tion is not as sim­ple. The mount­ing sys­tem alone is com­plex. A pair of V16-cylin­der diesels have enough torque to change the ro­ta­tion of the earth, so the mount­ing sys­tem is crit­i­cal and never a hap­pen­stance ar­range­ment. Then there are the heat ex­chang­ers that draw cool­ing wa­ter from through-hull fit­tings, the trans­mis­sions bolted onto the rear or front of the V-drive en­gine, prop shafts, pro­pel­lers and other run­ning gear suit­ably matched to the en­gine’s out­put. Swap­ping an out­board on a tran­som is a day at the beach com­pared to the work in­volved with chang­ing a diesel.

Nev­er­the­less, there are boat own­ers who make se­ri­ous plans to swap out an ex­ist­ing diesel when a more pow­er­ful model comes to mar­ket. As for the diesel en­gine man­u­fac­tur­ers, most—in­clud­ing MTU, Cater­pil­lar, MAN, Cum­mins, Volvo Penta and Yan­mar—are busy th­ese days build­ing new iron to quench the de­mand for more speed. “To­day’s trend is to­ward big­ger boats and more power, and en­gine builders will keep pace as the mar­ket dic­tates,” says Bob Shomo Jr., pres­i­dent of Off Road En­gines for MTU dis­trib­u­tor John­son & Tow­ers.

One thing to re­mem­ber, though, is that a horse­power rat­ing can be de­ceiv­ing. The horse­power out­put of a diesel en­gine on a fac­tory floor will dif­fer from the out­put pro­duced when that same en­gine is in the hull of a yacht, where the power pro­duced is then trans­ferred to the pro­pel­ler. Most crit­i­cal to re­mem­ber is that horse­power and en­gine weight con­trib­ute to per­for­mance. So, if you want more speed from a diesel-pow­ered boat, care­fully con­sider the ra­tio be­tween the two. One en­gine with a no­table ra­tio is MTU’s V16 2000M96L. “At some 10,000 pounds and 2,635 met­ric horse­power, it’s ac­knowl­edged as the ma­rine in­dus­try leader in its class,” says Shomo.

In the quest for speed, the en­gine-to-weight ra­tio is one point to ex­am­ine. Oth­ers in­clude hull dis­place­ment, load and pro­pel­ler con­fig­u­ra­tion. Con­sider Volvo Penta’s new in-line, six-cylin­der D13-1000 diesel, which de­vel­ops 1,000 horse­power with a con­ven­tional drive sys­tem and sin­gle prop. How­ever, when it’s com­bined with Volvo’s pod-drive sys­tem, the en­gine be­comes the IPS1350, which pro­vides more horse­power out­put with its for­ward-fac­ing ar­tic­u­lat­ing Duo­prop propul­sion.

The horse­power race among diesel man­u­fac­tur­ers is as much about speed as it is about ef­fi­ciency, ver­sa­til­ity and re­li­a­bil­ity. As a boat owner, con­sider your needs care­fully and you’ll find a so­lu­tion to match your ex­pec­ta­tions for power to zoom.

MTU’s V16 2000M96L has an ex­cel­lent pow­erto-weight ra­tio.

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