Good things take time, right? Isn’t that what your parents told you? OK, so they weren’t right about everything—you can be an instant lottery winner, and too much time on a hot barbecue makes a steak inedible—but when it comes to reliable high-performance engines, the maxim definitely applies.
Take the new MV8 570 engine from Ilmor Marine. The folks at the Plymouth, Mich., engine company trotted out the prototype of the 7.4-litre, LS-platform-based small-block powerplant more than a year ago at the 2012 Miami International Boat Show. And they just got around to installing the first production pair in a Formula 353 FAS3Tech sportboat two weeks before this year’s Miami event.
Of course, there’s more to the story—a lot more.
Almost two years ago, Ilmor began producing a catalyzed version of the 454-cubic-inch engine for well-known towboat builder MasterCraft.
“The story really started when General Motors announced it was going to drop the 8.1-litre platform completely,” said Paul Ray, president of Ilmor. “MasterCraft had been using Indmar versions of it in their larger towboats for some time.”
Rather than going with a supercharged 6.2-litre GM LSA aluminum engine platform, Ilmor offered MasterCraft an alternative: a normally aspirated, Ilmor-modified version of the 7.4-litre GM Racing LSX block.
“We did not want to develop the 6.2-litre engine for a number of reasons, supercharging versus going with a bigger, normally aspirated platform being one of them,” Ray explained. “We knew the engine had to be catalyzed. That was very important, and not just from an emissions requirement standpoint. A lot of these boats are being used for wake surfing, and the last thing we want is a wake surfer three feet behind a 500-plus-hp engine spewing carbon.
“We have almost 300 of those engines in the field right now,” he added. “They have been phenomenally successful and exceptionally reliable.”
With the catalyzed towboat engine proven, Ilmor set its sights on creating a similar but more powerful product for the high-performance powerboat market. Work began about a year after the first towboat engines began making their way into MasterCraft boats.
But because of the completely different duty cycles of go-fast boats and boats that pull wake surfers, wakeboarders, and waterskiers, the new high-performance version of the engine required modifications.
About the only stock GM parts on Ilmor’s 522-hp MasterCraft engine and its new MV8 570 non-catalyzed counterpart are its LS-3 cylinder heads and block. Like its lower-output siblings, all of the 570-hp engines are built by hand with parts custom-fabricated to Ilmor’s design specifications— including forged cranks, rods, and pistons. Even the “stock” LS-3 cylinder heads aren’t truly stock. Like the engine’s cast-iron GM Racing LS-X block, they are modified in-house at Ilmor.
While the majority of the internal components for both engines are the same, the calibration, compression ratio, and other elements Ray said he “won’t go into detail about” of the high-performance 570-hp model are different.
“As a fundamental package, the bottom end is the same for both engines,” said Ray. “But in towboats, you don’t run long at wide-open throttle, whereas in performance boats you do. The demands are more rigorous, so we had to make some changes for the 570, like adding an oil jet system to cool the pistons. Some of the changes we made are probably overkill, but some were absolutely necessary to make sure the valve train worked efficiently and reliably to keep producing the power.”
Another major change difference between the MV 570 and its lower-output towboat sibling? The 570-hp engine, which weighs 830 pounds and makes its peak 570 hp at 6,000 rpm, has a closed cooling system rather than an open freshwater system. Bore and stroke of the engine, which boasts a 10.7:1 compression ratio, are 4.185” x 4.125”.
“Every change we made between the catalyzed engine and the high-performance engine was a durability change based on different operating parameters,” Ray explained. “Closed cooling is pretty much standard on high-performance engines.”
On The Water
As the first marine writer to get a sea trial on the Ilmor MV8 570-powered 35-foot stepped-hull Formula sportboat, which weighed in at a hefty 9,600 pounds, I had the opportunity to sit down and talk with Alan Thomason, the technical director of Ilmor Marine, before our runs on Miami’s Biscayne Bay. Thomason has worked on the 570-hp, LS-based small-block engine project since it started.
“In a way, this engine is over-spec’d because from the beginning we had a vision of making more power with it,” Thomason said. “We were a little surprised at what we had to do with the oil system to maintain pressure at full [engine] speed, but that’s because this is a big-stroke version of an LS package—it’s a big-displacement engine in a small space.”
To that end, Ilmor created its own oil system for the MV8 570. The company even designed and manufactured its own pressure-relief valve and thermostat for the system.
On the water, the 35-footer felt strong with the power, especially in the middle of the operating range for the engines. According to Thomason, the rather spirited mid-range performance had everything to do with engines’ variable cam timing systems. “We designed and built the engine with that system to optimize its midrange performance,” he said.
With the engines turning 5,950 rpm, the hefty 9,600-pound stepped-hull boat reached a GPS-registered 81 mph. Total combined fuel consumption for both engines—the boat’s tanks were full of 93-octane gasoline, though the engines can run on 91-octane fuel—at wide-open throttle was 90 gallons per hour. With the engines turning 4,000 rpm and the boat running 52 mph, the total fuel burn was 35 gallons per hour.
To put the top-speed numbers in some kind of context, the same model with a pair of Mercury Racing 525EFI engines reportedly tops out at 78 to 79 mph. Though Formula also recently built a twin-engine Mercury Racing 565-powered 35-footer, that boat has not even begun the early stages of propeller testing and dial-in. So comparative numbers between the two engine packages of like power in the same platform do not exist.
The folks at Ilmor and Formula both readily admitted that the boat-and-engine combination is not completely dialed in. (At the time we ran the boat, it had less than nine hours of time on its 570-hp engines.) Everyone involved said they believe there are a few more miles per hour to be had on the top end. But everyone also said they were pleased with the early results.
Delivery of the first sets of Ilmor MV8 Ilmor engines to boat builders is scheduled to begin soon. According Ray, demand already exists. “The interest has been phenomenal,” he said. “Some companies have asked for ‘free engines,’ which we are not doing, and a lot of others have said, ‘Just call us when they’re ready and we’ll buy some.’”
Check out this video of the Ilmor MV8 570-powered Formula 353 FAS3Tech in action: