Mercury big-block is lighter and stronger

Posted on Written by Chris Landry

16_mercury_01The 8.2-liter gasoline engine is a drop-in replacement for the 8.1-liter model previously produced by General Motors

Pod drives and 4-stroke outboards have dominated the industry’s propulsion headlines for the last few years. This winter, however, Mercury Marine grabbed the spotlight with its new MerCruiser 8.2-liter big-block gasoline engine.

“I think it sets the standard for the next generation of inboard and sterndrive technology,” says MerCruiser brand director Facundo Onni. “With the durability and reliability of this engine and what it offers our customers, we think the 8.2 is best in its class in the industry for big-block power.”

The manufacturer introduced the V8 engine last fall at the Fort Lauderdale International Boat Show and showcased the engine’s performance in at least three boats – cruiser, runabout and performance models – at the Miami International Boat Show in February.

The 8.2 replaces the proven 8.1-liter 496-cubic-inch General Motors engine. “It was a very good engine for the marine industry and some other industrial applications,” says Onni. “However, it was not our decision to let it go. It was GM’s decision, so we had to come up with a replacement for it.”

18_mercury_02Its successor is a power plant with a 502-cubic-inch displacement that will be available in base (380 hp) and high-output (430 hp) versions. However, the closed-loop-cooled engine can spin up to 700 hp, says Onni. “We use it in a racing application,” he says. “Our 700 SCI with supercharger is 700 hp, so in its non-racing configurations the 8.2 will be using only slightly more than half of its full capacity.”

At Volvo Penta, the 8.1-liter engine will remain the big-block of choice for 2010. Volvo Penta has worked with GM to ensure its ability to supply the engine for sterndrive and IPS applications, according to Bob Apple, Volvo Penta senior vice president of sales and marketing.

“The 8.1 has been and continues to be a very reliable engine,” says Apple. “We are being very careful in our selection of a replacement, as reliability is one of the important requirements in our product range.”

Apple declined to provide more information about the company’s big-block plans after the supply of 8.1 engines is depleted.

More control

The 8.2-liter MerCruiser, which can be fueled with 87 octane gasoline, weighs 115 pounds less than the 8.1, despite its larger displacement, says Derric Drake, MerCruiser program manager for the new engine. In addition, it delivers more power and has better midrange acceleration, lower emissions and excellent fuel efficiency, says Drake. These improvements were possible because Mercury had more control over the design and components of this engine compared to its predecessor, says Drake.

“The 8.2 is probably the coolest thing we’ve done in a while from a sterndrive engine perspective because we’re in control,” he says. “With the 8.1, we received an assembled engine, but we assemble this right here.”

Mercury worked closely with the piston manufacturer Mahle to develop a proprietary piston design that reduces oil consumption, says Drake. The engine’s catalyzed exhaust system has a two-way catalyst, helping it earn an ultralow emissions rating. (Mercury offers its own synthetic oil designed for catalyzed engines.)

Other highlights include:

  • Mercury designed the air-intake system with a longer runner length that improves midrange torque, says Drake. The design forces more air into the cylinder when the intake valve opens, equating to more power, says Drake.
  • The aluminum cylinder heads are nearly identical to those on Mercury Racing’s 525 EFI engine for better power and weight savings, says Matt Jaeger, technical manager for Mercury’s product development and engineering. “The entire power cell – pistons, rings and connecting rods – help to improve fuel efficiency, reduce vibration and mitigate oil consumption,” says Jaeger.
  • With more control over engine assembly, Mercury was able to improve access to maintenance points. “We were able to move everything so it was high and forward,” says Drake. The oil fill, oil dipstick, oil filter and drive lube and steering fluid reservoirs are easy to see and access.
  • The engine is a drop-in replacement for the 496 (same footprint) with only a minor change to exhaust outlet location. The 8.2 uses the existing Bravo inner transom plate and steering assemblies.
  • The 8.2 engine is compatible with such MerCruiser options as Axius, SmartCraft, SeaCore and either digital or mechanical throttle and shift on the sterndrive models and DTS (Digital Throttle and Shift) on the inboard models.

The engine will not be available with Axius until this summer, when improvements to the joystick sterndrive system are expected to be finalized, according to Mercury. Like the pod-drive systems from Cummins MerCruiser Diesel (Zeus) and Volvo Penta (IPS), Axius uses joystick-controlled, independently articulating sterndrives for better maneuvering.

“There is some calibration that needs to be done before we marry Axius to this engine,” says Onni, the brand director. “We have to make sure all the systems fit.”

For instance, Axius uses more electrical power compared to a conventional helm setup, he says. “It draws more current, so we have to make sure it has enough current to charge the batteries,” says Onni. The Axius upgrade will apply to MerCruiser’s small-block engines as well, he says.

Details of the improvements were unavailable, but Onni did say the updated Axius system will be less complex, easier to install and just as reliable.

This article originally appeared in the March 2010 issue.

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