If you’re looking at a new stern-drive boat, it will almost certainly be powered by either a MerCruiser or a Volvo-Penta. In a few odd cases you might find an Ilmor here and there in serious high performance boats, but for the most part, one of these two big suppliers is going to provide the engine and drive for most runabouts, small to mid-sized cruisers, and speedboats. In many cases the boatbuilder will only supply one brand or the other, so you won’t have any say in the matter. But in other cases, the choice will be left up to you—so which will it be, a Mercruiser, or a Volvo-Penta?
The first factor you need to consider is the size of the boat, and the amount of power you need.
Mercruiser has a larger and more comprehensive line-up, starting with a 3.0L 135-hp. in-line four. This powerplant comes in TKS and MPI ECT versions; the TKS is a simpler carbureted rig, while the MPI ECT is a souped-up version with goodies like multi-point electronic fuel injection and SmartCraft CAN capability.
The line then moves up to Merc’s 4.3L 190-hp V-6, which comes in the same two TKS and MPI ECT classes, with the MPI ECT rating boosted to 220-hp. Merc’s mid-sized range includes a series of three V-8 models, a 5.0L MPI ECT that puts out 260-hp, the 5.7L 350 MAG ECT which creates 300 horses, and the 6.2L 377 MAG ECT which is rated at 320-hp. At the top of the heap lies the 8.2L MAG ECT (380-hp) and the MAG H.O. ECT (430-hp). For anything bigger, you've got to go to Mercury Racing.
Volvo-Penta more or less invented the production stern-drive with its Aquamatic in 1959. Due to price spikes the company trimmed back its offerings in 2011, eliminating their series of four-cylinder 3.0L engines which competed directly with—and were based on the same GM block as—Mercruiser's “entry level” offerings. The new requirements for catalytic converters on engines of this size boosted cost by around $2,000, and rather than fight the current, Volvo simply eliminated the 3.0 from its line. It’s interesting to note that this price spike has also boosted the popularity of small outboard-powered bowriders, which traditionally were powered by stern drives.
Today, the Volvo-Penta range starts with three 4.3L V-6’s (one 200 and two at 225-hp), which, like the MerCruisers, are offered in simple and more advanced configurations. Stepping up to 5.7L and 6.0L V-8s, Volvo has a wide range of engines, again available in simple and advanced configurations, including 225, 270, 300, 320, and 380 horsepower versions.
Fuel economy for the Mercs and Volvos are comparable across their lines; going back through years of boat reviews and performance tests shows that neither brand holds much of an advantage in this regard. What about reliability and consumer satisfaction? According to the annual J.D. Powers and Associates Marine Competitive Information Engine Study, which measures consumer satisfaction by contacting thousands of new-boat owners, Mercury and Volvo-Penta regularly run in a dead heat—in 2009, for example, they were separated by just three points on a scale of 1,000.
One area in which MerCruiser has an advantage is in the availability and cost of repairs and parts. There are MerCruiser dealers and MerCruiser mechanics virtually everywhere you find boats, but depending on where you live, finding a Volvo location can be a bit tougher and the parts can be a bit pricey.
On the flip side of the coin, Volvo-Penta drives have a well-deserved reputation for shifting the smoothest, and rough shifting is among the top complaints of stern drive owners. Volvo-Penta also has a more straightforward warranty program, offering coverage for two years or 600 hours, whichever comes first. Some MerCruiser models get only one year, some get as much as three, some vary depending on the boatbuilder, and some only apply when the engine is bought new as part of a boat-motor-outdrive package.
So: which one takes the cake? Both, and neither. In this highly competitive market, if either builder turned out a clearly inferior product it surely wouldn’t last long. As to which one you should choose, beyond the differences mentioned above it’ll depend to a large degree on what brand of boat you choose, where you live, and the relationship you have with your local dealer. Only one thing is for sure: if you’re buying a new boat with stern drive power, it’s a good bet you’ll have either a MerCruiser or a Volvo-Penta under the enginebox.