To find out, we worked with Hartsville, S.C.-based StingrayBoats to test each drive on the same 225SX (see sidebar onpage 37) powered by a 320-hp MerCruiser 377 Mag MPI with acatalytic converter. Testing with the 23-footer took place onLake Robinson, a few miles away from the Stingray factory. There are two companies offering both single-prop and dual-prop drives—MerCruiser and Volvo Penta. Wisconsin-basedMerCruiser has three basic single-prop drives, including theAlpha One, Bravo One and Bravo Two. Its dual-prop drive is theBravo Three.

So you’ve done your research, shopped around, and nowyou know exactly which boat you want. But the dealerhas two of that model in stock—one with a single-prop

sterndrive and the other with a dual-prop sterndrive. Which would you choose? Naturally, the dual-prop drive isgoing to cost more—$572 over the single-prop drive in the caseof the Stingray 225SX we tested. Yet, what do you gain or lose with each drive? In other words,how well do either of these drives transfer power from the engineto the water?

TO HELP YOU CHOOSE BETWEEN A SINGLE-PROP AND DUAL-PROP STERNDRIVE,WE ARRANGED TO RUN EACH ON THE SAME 23-FOOT SPORT CUDDY

PROPULSIONSTINGRAY 225XS

TRAILER BOATSTEST

BRAVOONE

BRAVOTHREE

34 TRAILER BOATS MAY 2011

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MAY 2011 TRAILER BOATS 35

Virginia-based Volvo Penta classifies its single-prop drive as theSX, and its Duoprop drive carries the DPS designation. Since it’s the most popular sterndrive brand in the U.S., weopted for MerCruiser products on the 225SX. For the single-prop testing, we used a Bravo One, and for the dual-prop testing,a Bravo Three. Because they share the same lower-unit profile, wefelt this provided the best apples-to-apples comparison.

WHY TWO PROPS?Volvo Penta was the first to introduce a dual-prop drive—theDuoprop—in 1982. It was one of the biggest events of thatdecade for boaters. MerCruiser followed years later with its BravoThree, once Volvo’s patent protection expired on the design. Both designs consist of twin counter-rotating propellers,which grip the water more tenaciously than a single prop. With

IT DIDN’T MATTER WHICH DRIVE, THE BRAVO ONE ORBRAVO THREE, MERCRUISER’S 377 MAG POSTED THESAME FUEL CONSUMPTION RATE AT WOT OF 25.2 GPH

BY JIM HENDRICKS

greater blade area and the leading prop delivering a superchargedstream of water to the trailing prop, this design tends to producegreater thrust and faster acceleration. According to Volvo Penta, the counter-rotating propellerseliminate the lateral forces existing in conventional single-propsterndrives. That means the engine’s energy and power isconcentrated on driving the boat forward vs. sideways, and thisincreases efficiency, which should translate to greater mpg. Also, while boats with single props tend to “heel over” or listto port at speed, the equalizing effect of counter-rotating dual-prop drives helps eliminate this undesirable characteristic. Thisalso leads to straighter tracking. While cornering at speed, dual-prop drives also tend tomaintain a better grip than single props as a result of lessaeration during hard turns.4

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In addition, the greater blade area and equalization of proptorque offer better low-speed maneuverability. And in reverse,dual-prop drives are much more predictable, largely eliminatingthe tendency to “crab.”

DUAL-PROP DOWNSIDESWith so many advantages, what are the downsides of dual-propdrives? One that we have already mentioned is cost. Expect topay about $500 to $1,000 more for the same boat equipped witha dual-prop drive. Complexity is another downside. Because of this, if somethinggoes wrong, it will cost more to fix it. Props are another costissue—if you wreck them, you are buying two vs. one for a single-prop drive. Finally, there is the subject of top speed. It is generally believedthat dual-props are slower on the top-end, primarily because ofthe additional drag created by the greater blade area. Yet, this is all theory. All other things being equal, how does adual prop fare against a single prop in real life? Let’s take a look. All of our testing took place on the same autumn day, withtemperatures in the low 60-degree range, and wind velocity ofapproximately five mph.

ACCELERATIONIn this test, the dual-prop Bravo Three was quicker, but not by

From left: Stingray’s new 225XS sport cuddy model features a wraparound helm with full instrumentation set it a burlwood panel. Although small, you can overnight in the cuddy cabinor utilize it for changing into a bathing suit or using the portable marine head. The integrated swim platform included an optional MB Quart remote and drive trim control mounted to port.

PROPULSIONSTINGRAY 225XS

TRAILER BOATSTEST

much in our standard 0-to-30-mph acceleration drill. The 3,200-pound Stingray (with 20 gallons of gasoline in thetank) vaulted to 30 mph in 5.8 seconds with the Bravo Three vs.6.0 seconds with the Bravo One. In 0-to-40- and 0-to-50-mph tests, the dual prop’s accelerationdifference did not grow appreciably. To 40 mph, it had a 0.2-secondadvantage, and to 50, it had a 0.4-second advantage. In this particular case, on this particular boat, it would seemthat the Bravo Three is a bit underwhelming when it comes toimproving acceleration. On a heavier boat, we would expect tosee more pronounced acceleration advantages with the dual-prop drive.

TOP SPEEDThis is the area where we expected the single-prop drive to shine,and indeed it bested the dual-prop drive by more than 2 mph.Average top speed for the Bravo One was 63.5 mph vs. 61.2 mphfor the Bravo Three. So if it is top speed you want, there is no question that theBravo One is faster than the Bravo Three. We should say here that Don Christman, Mercury Marine’stechnical representative, did quite a bit of propeller testing withboth drives prior to the final showdown, so prop-wise, the driveswere dialed in, though both were set at the same X-dimension(drive height) of 14.5 inches above the bottom of the transom.4

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MAY 2011 TRAILER BOATS 37

ENGIN

E/RPMSPEED/M

PH

FUEL/GPHFUEL/M

PGRAN

GE/MILES 1

ENGINE AS TESTED

Make (w/catalyst) MerCruiser 377 Mag MPI

Horsepower 320

Number of cylinders V-8

Displacement 6.2L (377 cid)

Induction Multi-point electronic fuel injection

WOT rpm range 4400-4800 rpm

DRIVES AS TESTEDBravo One Bravo Three

Weight 993 lbs. 1,019 lbs.

Gear ratio 1.50:1 2.00:1

Propeller

TEST RESULTS

Top speed (mph) 63.5 61.2

ACCELERATION (seconds)

0 to 30 mph 6.0 5.8

0 to 40 mph 8.1 7.9

0 to 50 mph 11.2 10.8

CONTACT INFORMATION

Stingray Boats, Dept. TBM, 625 Railroad Ave., Hartsville, SC 29550;843/383-4507; stingrayboats.com

MerCruiser, Dept. TBM, P.O. Box 1939, Fond du Lac, WI 54936;800/637-2879; mercurymarine.com

5.4 1.1 3.0 154 5.8 1.7 3.4 174

6.9 3.1 2.2 113 8.0 3.4 2.4 123

9.0 4.8 2.0 103 19.5 4.6 4.2 215

25.4 5.5 4.6 236 26.4 5.3 5.0 256

33.0 8.0 4.1 210 33.7 7.8 4.3 221

41.4 10.7 3.9 200 40.5 10.6 3.8 195

48.6 14.6 3.3 169 49.3 14.7 3.4 174

56.0 19.0 2.9 149 55.0 20.2 2.7 138

63.5 25.2 2.5 128 61.2 25.2 2.4 123

1000

1500

2000

2500

3000

3500

4000

4500

5000 (WOT)

Laser II137⁄8 x21" stainless

three-blade

g Bravo One g Bravo Three1Based on 90 percent fuel capacity

Bravo Three15/131⁄2 x 28" stainless

four/three-blade

The average top speed for the 23-footer with thesingle-prop Bravo One drive was 63.5 mph vs.

61.2 mph with the dual-prop Bravo Three drive.

Stingray’s new 225SX sport cuddylooks nearly as racy at the dock

as it does streaking across the lake.

This 23-footer rides on Stingray’s

next-generation Z-plane hull, and aswe have learned well over the years,these bottoms make the most ofavailable power. The 225SX is noexception. It lifts exceedingly wellat just a touch of trim, and rides highat full speed.

We found the mock hood scoop

and racing stripes on the foredeckslightly out of character for Stingraymodels, and later learned that is wasinspired by Stingray President AlFink’s affinity for fast cars.

A muscle car theme also is

reflected in a pair of swivelingbucket seats (each with flip-upbolsters) behind a steeply raked,low-profile windshield. A walk-through in the middle allows you toaccess the foredeck via two stepsabove the cuddy companionway. Butwatch that first step up—it’s a doozy.

Also lending the 225SX the air of a

fast car is the wraparound helm withfull instrumentation set in a burlwoodpanel, a tilting steering wheel withstainless spokes and a sound systemcontrol pad. Unlike most musclecars, the dash has a compass—ourcompliments on this addition.

The cuddy cabin is pretty tight.

You can overnight there in pinch, butit also affords a degree of privacy forchanging into a bathing suit or usingthe portable marine head.

The rear bench seating and cool-

looking upholstery detail on the aftsun pad also lend a high-performancefeel to this boat. Remove the centerpad to use the nonskid walkway tothe integral, stylishly sculpted swimplatform, which features a concealed,foldaway boarding ladder and a ski-tow eye.

Kudos to Stingray for coming

forward with a performance look tomatch the actual performance ofthis boat. We predict no shortage ofinterest among boat buyers in thenew Stingray 225SX.–JH

STINGRAY 225SX

Base price(w/Volvo Penta 4.3 GXi/SX) $37,716

Price as tested(w/MerCruiser 377 Mag MPI/Bravo 1) $50,214(w/MerCruiser 377 Mag MPI/Bravo 3) $50,786

Length 22'11"

Beam 8'4"

Deadrise at transom 20 degrees

Weight (dry) 3,204 lbs.

Draft (drive down) 33"

Fuel capacity 57 gals.

Maximum horsepower 320

NMMA certified Yes

NOTABLE STANDARD EQUIPMENTStainless bow, spring and stern pull-up cleats,built-in cooler, LED cockpit lighting, 180-wattMB Quart marine audio system, removablecockpit table, portable marine head

NOTABLE OPTIONAL EQUIPMENTSnap-in carpet, transom stereo remote,solid-color hull and deck, hull graphics

TEST NOTES>> Slight acceleration gains with Bravo Three

>>Bravo One offers best top speed by 2 mph

>> Greatest range comes at 2500 rpm withBravo Three

>>On this boat, Bravo One is a better choice

SPECIFICATIONS

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38 TRAILER BOATS MAY 2011

Official marine battery of fishing legend, Jimmy Houston

The Bravo Three was equipped with a 28-inch-pitch Bravo Threestainless prop set (15-inch-diameter, four-blade, left-hand frontprop; 131⁄2-inch-diameter, three-blade, right-hand rear prop). Onthe Bravo One was a 21-inch-pitch (137⁄8-inch-diameter) Laser IIstainless three-blade wheel.

FUEL EFFICIENCYWhen it comes to cruising range, the Bravo Three wins, postingnearly 0.5 mpg better than the Bravo One. Both found optimumcruise at 2500 rpm, but the Bravo Three was one mph better atthat efficiency point, achieving 26.4 mph while getting 5.0 mpgfor a range of 256 miles, with 10 percent fuel left in reserve. At the lower rpm ranges, the Bravo Three also was moreeconomical, and it planed at a lower rpm—2000 vs. 2500 rpmfor the Bravo One. This difference is due entirely to the efficiencyof the dual-prop drive. As the engine reached the higher rpms, the two drives wereneck and neck, through the Bravo One posted a slightly bettermpg at wide-open throttle. This is the result of the greater speedof the single-prop drive, as the 377 Mag posted the same fuelconsumption rate at WOT of 25.2 gph with either drive.

HANDLING & MANEUVERABILITYThese attributes are difficult to quantify, but definitely can befelt as you tool around the lake and pull into the marina. In ourtesting, there was no doubt that the Bravo Three-equippedStingray cornered and maneuvered better than the Bravo One. In hard turns at speed, the Bravo Three held its bite on the

water, and we really did not need to be trim it down during ourcornering tests. With the Bravo One, on the other hand, the propwould blow out and aerate if we did not trim the drive downduring sharp turns. The Bravo One also had a slight tendency to list to port whileunder way, while the Bravo Three tended to remain on an evenkeel. Many boats have trim tabs to help compensate for suchprop torque, so we don’t see the Bravo One’s tendency to heelover as a major disadvantage. However, we do see the Bravo Three’s predictability in slow-speed situations as a major upside of this drive system. Itanswers the helm immediately, and the equalization of proptorque lets you maneuver precisely, whether in forward or reverse.The Bravo One isn’t bad, but the Bravo Three is much better.

CONCLUSIONJust one look and you can tell that Stingray’s new 225SX is aboat built for speed. With that in mind, and given the additionalcost and complexity of a dual-prop drive, we believe that asingle-prop drive such as the Bravo One is best suited for thisparticular model. Yet, the Bravo Three gets you a tad better acceleration, greaterfuel efficiency and improved handling, but on a boat of this sizeand demeanor, we think you can do without it. On a bigger, heavier boat, however, dual-prop drives are muchmore worthwhile, particularly when it comes to maneuverabilityand fuel economy. That is when the efficient transfer of powerreally counts. TB

PROPULSIONSTINGRAY 225XS

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