TEST RESULTS1   (mph) (mpg) Model Merc Volvo Merc Volvo   4.3 MPI/A1 4.3 GXi/SX 4.3 MPI/A1 4.3 GXi/SX (rpm)   1000 5.9 5.5 4.2 4.2 1500 7.6 7.3 2.9 3.0 2000 9.0 19.0 1.9 4.3 2500 28.5 29.2 5.6 6.1 30002 36.0 36.9 4.9 5.3 35003 44.2 44.2 4.9 4.5 4000 51.6 52.9 4.2 4.2 4500 58.3 59.7 3.6 3.5 47004 59.9   3.7   48005   60.6   3.4 1 w/ two adult males aboard 3 Optimum cruise-Merc 5 WOT for Volvo 2 Optimum cruise-Volvo 4 WOT for Merc ACCELERATION (seconds) Model MerCruiser Volvo Penta   4.3 MPI/Alpha 4.3 GXi/SX 0-20 mph 5.0 4.8 0-30 mph 7.2 6.8 0-40 mph 9.8 9.3 0-50 mph 13.2 13.2 SPECIFICATIONS Model MerCruiser Volvo Penta   4.3 MPI/Alpha 4.3 GXi/SX Horsepower 220 225 Cylinders V-6 V-6 Displacement 4.3L/262 cid 4.3L/262 cid Induction Multi-port EFI Multi-port EFI Gear Ratio 1.62:1 1.60:1 Propeller Mercury Laser 13 3/4"x23" ss 3-blade Volvo Penta 14 1/4"x23" ss 3-blade Weight 865 lbs. 907 lbs. Price1 $22,574 $22,561 Address Merc Dept. TBM 3003 N. Perkins Rd Stillwater OK 74075 920-929-5040; mercurymarine.com Volvo Dept. TBM 1300 Volvo Penta Dr Chesapeake VA 23320 757-436-3800 volvopenta.com 1MSRP of Stingray 195LR w/ corresponding sterndrive package TOP SPEED (mph) Average with one adult male aboard MerCruiser 4.3MPI/Alpha 60.9 mph Volvo Penta 4.3 GXi/SX 61.6 mph KEY DIFFERENCES While MerCruiser and Volvo Penta use the same 4.3L electronic-fuel-injected engine from General Motors, there are a number of variations in these sterndrive packages. Aside from different drives, here are some key differences. Model MerCruiser Volvo Penta   4.3 MPI/Alpha 4.3 GXi/SX Propshaft HP 220 225 Gear Engagement Dog Clutch Cone Clutch Electronic Control Motorola 555 GM MEFI IV Alternator 65 amp 75 amp Digital Gauge Opt. SmartCraft None Available Recommended Fuel 87-octane gas 89-octane gas Limited Warranty 1-year 2-year

One of the most plentiful engines ever produced is the General Motors 4.3L V-6. In addition to finding its way into many GM cars and trucks, this engine has also become a standard powerplant in many boats.

Fact is, any boatbuilder that makes 17- to 22-foot sterndrive-powered boats is likely to offer the 4.3L in one form or another as standard or optional power.

Both MerCruiser and Volvo Penta offer versions of the V-6. Each has carbureted and electronic-fuel-injected (EFI) models in its lineup. While GM delivers the same basic powerplant to both, MerCruiser and Volvo Penta take slightly different approaches in marinizing the engine and bringing it to market. The biggest difference in these sterndrive models lies in the outdrive configurations. Many 4.3L Mercs are fitted with the popular Alpha drive, while the Volvo often sports the similarly popular SX drive.

With this in mind, we thought it would be interesting to test the two EFI powerplants side by side to compare performance in terms of acceleration, top speed and fuel economy. To accomplish this project, we enlisted the aid of South Carolina-based Stingray Powerboats. Company president and founder Al Fink graciously had each powerplant installed in identical 195LR bowriders. The 195LR is a new model for 2004 and boasts the company's next-generation Z-plane hull design (see Test Platform sidebar below).

TEST PARAMETERS
We invited representatives from each engine company to be present during our testing on South Carolina's Lake Robinson near Stingray's headquarters in Hartsville — this to help ensure that the engines and drives were operating at peak performance. Assisting us in this regard were field technicians Don Christman from Mercury Marine and Mark Huddleston from Volvo Penta. To their credit, both men not only worked hard in their respective areas, but their amiable spirit made our project all the more pleasant.

To make sure there was no disparity in driving skills and driver weight between the Merc- and Volvo-powered Stingrays during our acceleration and top speed runs, we used the same test driver in each boat. That task fell to tireless Mike Weatherford, who has been with Stingray since its inception and knows how to finesse each of the company's 18 models for optimum performance. Weatherford was the only occupant in the boat during these runs. The fuel economy numbers, however, were gathered with two people in each boat. We recorded the data while Christman and Huddleston drove their respective boats. Hence the top speed is different in the fuel data figures than it is in the solo-occupant acceleration and speed runs.

To record our performance data, we used a Stalker Acceleration Testing System, which combines the Stalker ATS Professional Radar Gun with a special Stalker ATS computer software program. The gun measures the speed of the boat at precise intervals, and then sends that data to the computer through a cable. The software program assigns time information and then calculates distance and acceleration rates for each fraction of speed recorded.

Since speed, time, distance, and acceleration are mathematically related, having any two of these measurements means the other components can be derived with absolute accuracy, and the software contains the formulas to accomplish this. The software allows you to record a radar gun, then display the information graphically in any combination of speed, time, distance, and/or acceleration. It does it all instantly.

Since the entire system is portable we were able to set up a makeshift office right at the dock on Lake Robinson with a battery pack and two 5-gallon barrels, one serving as a table for the laptop and another to sit on. Crude, but effective.

PLAYER INTRODUCTIONS
Each manufacturers' sterndrive package has certain advantages over the other. MerCruiser's 4.3 MPI with the Alpha drive has a weight advantage, tipping the scale 42 pounds below Volvo Penta's 4.3 GXi with the SX drive. On the other hand, Volvo Penta says the SX's added underwater gearcase length increases stability, improves handling and positions the propeller farther aft for a stronger bite, resulting in quicker acceleration.

GM Powertrain indicates that the Vortec 4300 marine engine it supplies is rated at 223 hp, which is 13 to 23 hp more than the automotive versions. Volvo Penta then calibrates its 4.3 GXi to be 225 hp at the prop, while MerCruiser rates its 4.3 MPI at only 220 hp at the prop. We did not check either engine on a dynamometer.

Once of the biggest differences between the two offerings is the choice of electronic control module (ECM) technology to operate engine functions. Volvo Penta uses GM's MEFI IV, a fourth-generation ECM that uses hybrid technology to optimize fuel and spark. MerCruiser, on the other hand, uses the 555 ECM from Motorola, which makes it compatible with Merc's SmartCraft system.

SmartCraft is a sophisticated technology that can link the boat's power, systems and controls with a variety of other sensors to provide everything from engine diagnostics and fuel management to digital throttle and shift control.

Another key difference is that MerCruiser uses a dog clutch in its Alpha gearcase, while Volvo Penta uses a cone clutch in the SX. The result is the SX drive shifts smoother, and by all counts, should last longer. The Alpha drive shifts best when it is put in gear quickly; as with an outboard, don't try nursing it. You'll just grind the gears. It should be noted that MerCruiser only uses a dog clutch on its Alpha drive; all other Merc outdrives utilize cone clutches.

In our testing, we mated the MerCruiser drive with a Mercury propeller and the Volvo Penta drive with a Volvo Penta propeller. No propellers from other manufacturers were included in this test. Both propellers were stainless steel three-blades with 23 inches of pitch.

LET THE GAMES BEGINS
In terms of acceleration from a dead standstill, the Volvo Penta boat reached 20 mph in 4.8 seconds, compared with 5 seconds for MerCruiser—a mere 0.2 second advantage.

The Volvo Penta continued to out-accelerate the MerCruiser by reaching both 30 and 40 mph a half-second quicker. Interestingly, however, the MerCruiser boat closed the gap past 40 mph, with both boats reaching 50 mph at the same time: 13.2 seconds. The bottom line is the Volvo Penta accelerates quicker out of the hole, but the MerCruiser comes on strong in the stretch.

At top end, the Volvo Penta won. We ran each boat in two directions (toward us and away from us) and averaged the top speed. Volvo Penta posted an average speed of 61.6 mph. MerCruiser, on the other hand, recorded an average of 60.9 mph.

The final part of our test involved fuel economy. Volvo Penta netted the best miles-per-gallon usage at slow to medium engine speeds up to 3000 rpm, which corresponds to boat speeds in the 35 to 40 mph range, where the craft will likely be run most of the time. At 2000 rpm, the Volvo Penta-powered boat was able to plane, whereas the MerCruiser boat was not. Hence, you see a substantial difference in fuel usage at that point. At 3500 rpm, where both boats ran 42 mph, MerCruiser took a slight edge in fuel economy. At 4000 rpm, both boats were equal fuel-wise. But at top end, the MerCruiser recorded slightly better fuel economy.

EFFICIENCY vs. ECONOMY
It should be noted when discussing fuel economy between these two sterndrive packages that Volvo Penta recommends using fuel with a minimum octane of 89, while MerCruiser recommends 87. The dollar cost at the pump between 87- and 89-octane fuel should be taken into consideration when comparing the true economy of one engine over the other. In other words, while Volvo Penta may use less fuel throughout much of the rpm range, the actual cost may not be that different.

All things considered, the Volvo Penta edged out the MerCruiser in this contest. But the margin of victory was not overwhelming, so other factors may also influence your buying decision one way or the other. For example, Merc offers the SmartCraft digital instrumentation upgrade, while Volvo does not currently have such an upgrade. MerCruiser also has a wider national service network.

However, if it's bragging rights for fastest boat you desire, Volvo gets the nod.

Randy Scott