Since its introduction more than 10 years ago, the 525 EFI has been the workhorse of the Mercury Racing engine line. In addition to being the most popular “entry-level” engine for new high-performance powerboats—and most often they travel in pairs— the 525 EFI mill was the “spec” engine for a number of offshore racing classes, including Super Cat Lite (a twin-engine class that was eliminated in 2013) and Superboat Vee (a single-engine V-bottom class that is still standing).

The 540 engine is replacing Mercury Racing’s venerable 525 EFI powerplant.

The 540 engine is replacing Mercury Racing’s venerable 525 EFI powerplant.

Without question, the 525 EFI was one of the most successful models in the history of the Fond Du Lac, Wis., high-performance marine engine company.

But the release of the new Mercury Racing 540 at this year's Miami International Boat Show spelled the end of the line for the 525 EFI. In late 2013, the company introduced its 520 engine. For all intents and purposes, the 540 engine is a 520 model with headers, which enhance exhaust efficiency and add horsepower.

Thanks to larger cylinder bores, the naturally aspirated 8.6-liter engine has a 21-cubic-inch displacement advantage—523 cubic inches as opposed to 502 cubic inches—over the 525EFI model. This larger displacement produces 13 percent more planing torque and an additional 50 foot-pounds of peak torque, according to a press release from the high-performance marine engine company.

"The 540 enhances performance people have come to know from the 525 with consumer friendly features such as digital throttle and shift," said Rick Mackie, the senior marketing manager for Mercury Racing. "It shares the same computer as the 565 and this outshines the 525 in fuel efficiency and range as well."

Based on a CNC-machined cast-iron block, the closed-cooled engine boasts internal components including a balanced crankshaft, forged and shot-peened I-beam connecting rods, forged aluminum pistons, and Mercury Racing aluminum cylinder heads with optimized valve angles for improved air flow.

The computer-controlled engine uses the same Propulsion Control Module (PCM 09) microprocessor as the 520 and 565 engines, as well as the 1,100-, 1,350- and 1,650-hp QC4v engines. In addition to the engine tuning, performance and operational benefits, the controller makes the 540 compatible with Mercury Racing's new fully digital Zero Effort controls.

The 540 can be paired with the company's new Bravo One XR Sport stern drive. The drive's surface-piercing gear case is two inches shorter than a standard Bravo unit. For improved overall cooling, the new drive is equipped with dual water pickups mounted on the nose of the torpedo and strut.