Ilmor High-Performance Marine’s New Big-Block Offerings

Ilmor vies for a bigger share of the high-performance market.

In the high-performance realm, Mercury Racing ( dominates. Oh, sure, there are “boutique” engine builders such as Sterling Performance ( and Teague Custom Marine ( Yet, no one matches Merc Racing’s product range and service network, right?

Hold your horses. Now there’s a challenger: Ilmor High-Performance Marine ( believes it has the engine/drive packages, as well as the customer service, to give Mercury Racing a run for its money.

The parent company, Ilmor Engineering Inc., started in 1983 by building engines for the IndyCar racing series. Nine years later it introduced its first high-performance marine engines. Based on the Dodge Viper V-10, Ilmor’s MV-10 line now includes five horsepower choices: 570, 625, 650, 700 and 725. Ilmor also offers six V-8 models in its recreational series.


Strong and Clean
The latest from Ilmor are the Generation IV V-10 and the company’s new Indy surface-piercing drive. Available in 650 hp and 725 hp versions, the sophisticated 511-cubic-inch aluminum power plant is naturally aspirated and meets California Air Resources Board emissions regulations for high-performance marine engines. Get this: It does so without a catalytic converter.

With closed cooling and stainless-steel headers, the Gen IV features Ilmor’s ICE NMEA 2000-compatible engine control system and twin electronic drive-by-wire throttle bodies for easy monitoring and deft control.

Ilmor’s Indy sterndrive was built to handle the torque of the new engine, while also creating the smallest “bullet” shape possible. The engine/drive package weighs in at 1,236 pounds. Merc Racing’s 700 SCi with an NXT drive weighs 1,548 pounds, a 600-pound difference for twin-engine boats.


So far, Ilmor’s 725s (available in five colors) have found homes largely in semicustom boats from builders such as Advantage, DCB, Eliminator, Hallett, Howard, Outer Limits and Skater. Recently, however, Formula Boats put a pair of 725s with Indy drives in a 400 FX8, and we had the exclusive opportunity for a test drive on Lake Michigan.


Smooth Shifting
The engines shift seamlessly into gear. No clunk. This is due to Ilmor’s hydraulic dry-sump transmission design, which transfers each engine’s 650 foot-pounds of torque to its respective drive.

The drives were set up conservatively with the props spinning outboard (versus inboard). To help the 23-inch-pitch Hering forged stainless, six-blade cleaver props spin up quickly, the drive plates were fitted with tubes above that induce ventilation. The props hooked up nicely at about 3,500 rpm and 32 mph, just as the vented hull also began to air out.


With Scott Boss, owner of Dry Harbor Marine in Charlevoix, Michigan, at the wheel, our time to plane was 11.66 seconds, and we reached 30 mph in 16.79 seconds. Zero-to-40 mph time was 22.55 seconds. We kept the trim tabs up but used the Ilmor programmable trim system to optimize the drive angles.

10 Tons Going 70
This was a heavy boat with an 11-foot beam, carrying 250 gallons of gas, 50 gallons of water, a three-person crew and lots of gear. Total weight of the 41½-footer was around 21,000 pounds.

Cleaver-style props are not designed for acceleration, but rather top-end performance, and that is where the 725s showed their stuff. Running in one-foot chop with an air temperature of 70 degrees F in a light drizzle, the Ilmors hit their stride at about 5,000 rpm and 55 mph, and topped out at 6,400 rpm with a top speed of 70.05 mph, marking the first time that we’ve seen a Formula 400 reach such speed.


Ilmor claims the engines are relatively fuel-efficient, particularly at idle when the V-10 shuts down five cylinders to save gas. When it came to cruising, the Formula 400 FX8 found its optimum efficiency at 4,000 rpm and 45.2 mph, where the twin 725s burned 47 gph, achieving 0.96 mpg.

Service and Support
While Ilmor’s service network is growing, it’s not as wide-ranging as Merc’s. At the same time, Ilmor’s director of sales and marketing, Jessica Gamarra, says that if you have a favorite marina, the company will send out trained service personnel to talk to the mechanics. “We provide a high level of customer service,” she says. “We know all of our customers, and they can call and find someone available any time.”

The Ilmor 725 with the Indy drive is not cheap, though it is less than a comparable Merc package.Retail price for a single engine/drive is $86,800, excluding propeller. Count on about $6,250 for a Hering forged stainless prop. However, a Merc Racing 700 SCi/NXT carries a retail price of $90,903 excluding prop.

So it would appear that Merc Racing now has a challenger for dominance of the high-performance power market. We are going to enjoy watching this horse race.