Less than an hour ago, speedonthewater.com co-publisher and executive editor Jason Johnson and I hopped off the Formula Boats 353 FAS3Tech with the first production pair of Ilmor Marine MV8 570 engines. On board with us for our first impression of the 35-footer in the Government Cut section of Miami’s Biscayne Bay was Brian Smith of the Decatur, Ind., boat company and Bob Teague of Teague Custom Marine, Ilmor’s primary West Coast dealer and one of two suppliers—the other is IMCO Marine—of stern drives for the new engine.
Before we headed out, I had a chance to chat with Alan Thomason, the technical director of Ilmor Marine who has worked on the 570-hp, LS-based small-block engine project since its inception a little more than two year ago. (Read the story.) Thomason shepherded the 7.4-litre, 454-cubic-inch platform through its first phase of development as a catalyzed 522-hp MasterCraft towboat engine, so it’s safe to say he’s familiar with every aspect of it.
Bore and stroke of the engine, which boasts a 10.7:1 compression ratio are 4.185” x 4.125”. Maximum operating speed, as noted in previous articles on speedonthewater.com, is 6,000 rpm.
“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.
Another key highlight of the engine that Thomason pointed out was its variable cam timing system. “We designed and built the engine with that system to optimize its midrange performance,” he said.
Tight as the time frame may seem—an actually is—the Ilmor 570-powered 35-footer touched the water for the first time yesterday morning. Working with the boat’s 1.5:1 gear ratio drives from IMCO, Smith and company tried a number of different propeller options.
They started with 26”-pitch Mercury Maximus five-blade propellers, and could not get the clearly over-propped boat above 4,000 rpm. With four-blade 22”-pitch Mercury Bravo props, on the other hand, the boat was under-propped and on the rev limiters.
The best performance solution came in the form of 15-1/4” diameter Maximus 23”-pitch five-blade lab-finished wheels. It is safe to say, however, that with all of seven hours on the engines—including the 45 minutes of running time we logged—dial in is far from complete. A different gear ratio might permit the propulsion package to handle bigger-pitch propellers and produce a bit more top speed.
So we’ll answer the burning question first: With the engines turning 5,950 rpm, the 9,600-pound stepped-hull boat reached a GPS-registered 81 mph on the Mercury SmartCraft System View displays. 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.
A couple of purely subjective observations: With the small-block 570s, the 353, which everyone aboard had either driven or ridden in before, felt more nimble and stayed on plane at a lower speed than any of us could remember it doing with heavier—approximately 250 pounds heavier per side—big-block engines. Though we didn’t run numbers on it, midrange acceleration felt particularly strong.
Another subjective observation? At wide-open throttle, the MV8 570s crackled with sound, not unlike a string of firecrackers, in the most delightful way.
Delivery of the first sets of Ilmor MV8 Ilmor engines to boat builders is scheduled to begin in approximately six weeks. According to Paul Ray, the president of the company, that can’t happen soon enough based on the pent-up demand for the new powerplants.
“The interest has been phenomenal,” Ray 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.’
“People are generally enthusiastic about this engine,” Ray added. “And that’s good news. It’s been awhile since we’ve introduced a new product. Frankly, we think it’s a good thing that we offer a comparably powered product with completely different packaging from the only competitor we have in the smaller-engine category.”
Teague, who says he has been eagerly anticipating the release of the MV8 570 for the better part of two years, agrees.
“It’s always good to have options,” he said.
Editor's Note: The Ilmor 570-powered Formula 353 FAS3Tech will be on display this week at Sea Isle Marina during the 2013 Miami International Boat Show.
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