Completely designed and manufactured in house by Mercury Marine, the new MerCruiser 4.5L stern drive engine was unveiled in front of members of the national marine media moments ago during a press event at the company’s headquarters in Fond du Lac, Wis. Reportedly 130 pounds lighter than a V-8 5.0L small-block engine, the 4.5L pumps out 250 hp, which is comparable to the power output of its heavier 5L cousin.

Designed and manufactured in house by Mercury Marine, the new MerCruiser 4.5L stern drive engine was unveiled at press event this evening.

“There isn’t a single GM part on this engine,” said Brett Martin, a MerCruiser product application manager at Mercury Marine. “It’s not a marine engine based on an automotive platform, it’s not an LS engine. In the 18 years I’ve been here, I think it’s the best MerCruiser engine we’ve ever built.

“We saved a lot of weight on the intake manifold,” he added. “And the 4.5L can be freshwater or raw-water cooled.”

“We saved a lot of weight on the intake manifold,” he added. “And the 4.5L can be freshwater or raw-water cooled.”

“We are proud to introduce the next generation of stern-drive technology with this ground-breaking new engine,” said John Pfeifer, the president of Mercury, in a press release from the company. “This engine was purpose-built for marine use.”

Major components of the MerCruiser 4.5L engine include a newly designed rear-facing throttle body, anti-whistle throttle plate, engine cover and mounts, lightweight flywheel, fuel supply module and structural oil pan. According the release, all of those elements work together to deliver superior idle and smoothness and low noise and vibration.

“Mercury Marine has taken the initiative to design a lightweight, high-displacement V-6 marine engine that is not dependent on automotive technology,” said Buck Pegg, one of the founders of Chaparral Boats, in the release. “That is not just great, that is outstanding.”

The MerCruiser 4.5L is the first V-6 stern-drive that’s compatible with SmartCraft Digital Throttle & Shift for immediate throttle response and smooth shifting throughout the rpm band. An option for the 4.5L V-6 with DTS, Joystick Piloting provides easy docking and low-speed maneuverability.

The 4.5L V-6 also offers Adaptive Speed Control (ASC), which automatically maintains the set rpm point regardless of load or condition changes, such as tight turns, tow sports and lower speeds on plane. The result is increased throttle response and a “sportier” feel for the driver, according to the release, who no longer has to make continual throttle-control adjustments.

To guard the 4.5L V-6 from corrosion, the engine was built cast-iron componentry wherever the engine encounters seawater and corrosion-resistant aluminum and composites everywhere else. Digital rather than analog sensors are used throughout the engine. As with all MerCruiser engines, the 4.5L stern-drive comes with a standard three-year corrosion warranty plus Mercury’s limited manufacturer’s warranty of up to two years. The 4.5L can be installed in single- and twin-engine applications and is compatible with company’s full series of Alpha and Bravo drives.

At present, the 4.5L is purely a MerCruiser engine product. Mercury Racing, the largest manufacturer of high-performance marine engines in the world, is not adding a “high-output” version of the new MerCruiser stern-drive engine platform to its line anytime soon.

Said Erik Christiansen, Mercury Racing’s general manager, “We have no plans for developing anything off the (4.5L) platform at this time.”