Weighing a svelte 523 pounds, Raylar's aluminum LSM 550 engine produces an astounding 550 horsepower.

By Matt Trulio

Weight and horsepower aren't exactly fast friends. In fact, you could say they're mortal enemies. So the idea of a lighter engine that produces the same—or better—power than its heavier counterparts always has been appealing. The trick, of course, is executing that idea.

The folks at Raylar Engine Development believe they've pulled it off with their new naturally aspirated LSM 550 engine, which was released earlier this year after a full year of testing and development. And though we haven't tested one of the new all-aluminum creations—we caught our first glimpse of one at this year's Miami International Boat Show—we're looking forward to testing a boat with a pair of them in the near future. Without question, they show promise.

The LSM 550 takes its name from General Motors' LS engine platform architecture. The LS-based package powers Corvettes, the ultimate American muscle car, as well as most GM trucks. The "M" in the Raylar moniker stands for "Marine" and the 550, well, obviously, that's the horsepower rating.

As any gear head worth his weight in piston rings knows, aluminum is lighter than cast iron, which has been the traditional material used in marine-engine applications. And as that same gear head also surely knows, aluminum fairs poorly (i.e. deteriorates quickly) when directly exposed to saltwater. A saltwater cooling system that's just dandy for a cast-iron engine will destroy an aluminum engine in short order.

That's why Raylar's first order of business in development of the LSM 550 was to create a closed freshwater cooling system for the engine. That system was developed in concert with its Safeguard engine-control system, which monitors engine functions from oil temperature to water pressure and will put the engine in "limp-home" mode in the event of a critical problem.

Marinizing the 434-cubic-inch engine also required beefing up its essential internal elements.

"We are using all of our in-house-designed internal components like a forged 4340 bill crankshaft, specially designed MAHLE pistons and billet H-beam connecting rods," says Ray Broady, one of the owners behind Raylar.

"We put in special intake and exhaust valves, special valve springs and a special camshaft. We're using electronic variable valve timing—we're the only builder doing that in high-performance, heavy-duty marine engines. It's like having three or four different camshafts in the same engine. We can actually change valve-event timing based on rpm and engine load."

Raylar needed a stainless-steel four-tube header system for the LSM 550. Unfortunately there wasn't one sitting on an exhaust manufacturer's shelf, so the company designed its own and took production of that system in-house.

According to Broady, the rising price of gasoline provided the incentive to create the LSM 550 engine.

"The fuel economy of high-performance boats is coming more and more into question," he explains. "The industry is going to be moving away from the old iron big-block GM engines to these new families of aluminum engines, which are lighter, smaller and 20 to 25 percent more fuel efficient. With these engine families, we can make more horsepower with less fuel.

"The LSM 550 is more efficient than a comparable cast-iron big-block because it produces a higher horsepower-to-liter ratio," Broady continues. "Normally, in a cast-iron big-block you would need to be in the 500-cubic-inch range to produce the same level of horsepower we're producing with an engine that is just a little more than 400 cubic inches. Part of it is better breathing—these new families of engines have better cylinder head designs that use air more efficiently."

The LSM 550 idles 600 rpm with a peak of 5,600 rpm. According to Broady, the engine makes peak horsepower at 5,500 rpm and its peak 565 foot-pounds of torque at 4,400 rpm. At 3,000 rpm, the engine reportedly still makes 500 foot-pounds of torque.

"With electronic variable cam timing, we can build a torque curve that's almost like a diesel engine, but with a much wider rpm range," Broady says.

According to Broady, lower-displacement (360 and 370 cid) LS platforms likely will be the first offerings from the LS family to be marinized by other builders.

Broady says those lower-displacement engines probably will be supercharged to make the necessary power for high-performance marine applications, and because of that they will spend roughly 90 percent of their working lives in boost. That's why Raylar opted for natural aspiration in the bigger 434-cid (7.1-liter) platform.

"We go by the old saying, 'There's no replacement for displacement,'" he says.

But while the LSM 550 is big on the inside, it is relatively small on the outside. It reportedly measures 5 inches shorter, 4 inches narrower and 7 inches lower than a standard 496-cubic-inch engine.

It also weighs about half as much, meaning that a pair of LSM 550 engines replacing a pair of big-blocks in an engine compartment could yield a total weight savings of 1,000 pounds.

To make the LSM 550 even more attractive for buyers looking to repower their boats, Raylar designed the engine to be "plug and play" in small-block and big-block applications with Bravo drives. Cost of the custom-painted engine, including the headers and other hardware, is $26,873.

"We think it's going to be a great retrofit engine, especially for boats with old iron small-blocks," Broady says. "It's designed to be easily dropped in front of a Bravo drive without any difficulty.

"We wanted to be out with this engine a year ahead of the market," he adds. "We got it where we wanted to be."

Contact Information
Raylar Engine Development, 4645 Ruffner St., Suite G, San Diego, CA 92111, 866-496-8181, www.raylarengine.com