When Mercury Racing introduced its 400-hp, six-cylinder supercharged ROS outboard engine for the X-CAT racing series in November 2015, more than a few go-fast powerboat enthusiasts were convinced a high-performance pleasure version would soon follow. Their exuberance was natural—everyone loves the latest and greatest. But, as representatives of the Fond du Lac, Wis., consistently maintained, it wasn’t going to happen. And it didn’t.

Mercury Racing’s four-stroke V-8 360 APX outboard engine is a giant leap for the tunnel boat racing world. Photos courtesy/copyright Mercury Racing.

On rigging chores alone, the ROS outboard’s dry sump oiling system, which incorporates a scavenge pump underneath the powerhead and requires a remote tank in the boat, made the 400R outboard a superior choice for consumer applications. Still, a couple of ROS outboard-powered catamaran projects did move forward, both for well-heeled, experienced clients with extensive offshore racing and high-performance powerboating backgrounds who went in with clear eyes and open checkbooks.

Neither succeeded.

And so, with yesterday’s introduction of the four-stroke, V-8 360 APX outboard exclusively designed and produced for teams competing in the F1H2O tunnel boat racing series, the question among eager consumers arises again: When will Mercury Racing release a pleasure version?

Likely never, and the tunnel boat-racing engine’s gearcase, which has neither neutral or reverse, and its 12-inch midsection—far too short for most go-fast boat transoms—are but the most obvious hurdles for would-be buyers in the consumer world. Per the F1H2O tunnel boat-racing realm, the 360 APX also is set up with cable steering, which was long ago replaced by hydraulic or electro-hydraulic systems in the mainstream high-performance powerboat world.

To find out more, I turned to Jeff Broman, Mercury Racing’s unfailingly candid and affable director of engineering. In addition to noting all of the above as barriers to consumer applications for the naturally aspirated 360-hp outboard, he provided several others—starting with durability, something you probably wouldn’t have expected.

“The 360 APX is going to be a huge leap forward in terms of durability compared to the current 2.5-liter, two-stroke V-6 outboards (for the F1H2O series),” he said. “However, the durability hurdles a consumer engine must clear to be offered with a full factory warranty are even higher yet. When we evolved the 300R to the 360 APX, we made a conscious decision to trade some amount of durability for increased performance.”

That the 360 APX requires its fuel pump to be mounted inside the boat also doesn’t fly in the consumer outboard world. “This isn’t allowed for engines outside of competition use,” Broman said.

Noise and vibration, a of couple of less-than-desirable traits that Mercury Racing and Mercury Marine have spent hundreds of millions of dollars engineering out of their outboard engines, are two more impediments to consumer applications.

Exciting as the prospect may be, a consumer version of the 360 APX outboard engine is not on the horizon for a number of reasons.

“The 360 APX’s above-water exhaust—no intake attenuator—and ultra-lightweight cowl translate into a lot more noise for the operator and passengers than most customers would tolerate,” he said. “We eliminated the balance shaft and the torsional damper from the flywheel. Increasing the rpm also adds much more vibrational energy. The outboard is mounted directly to the transom assembly and there are no mounts to isolate it from the boat.”

Trim range is yet another issue, he explained. “The full trim range for the 360 APX is only 13 degrees, which is about 60 degrees less than that of the 300R,” he said.

Last but not least, the 360 APX has none of the “customer-facing” features that—once again—Mercury Racing and Mercury Marine have spent fortunes designing into their consumer outboards.

“We’ve removed some of the features that make our V-6 and V-8 families unique like the service door—with the 360 APX you have to remove the cowl to check the dipstick—and hidden cowl latch and oil sensor. Adaptive Speed Control, Advanced Range Optimization, and Active Trim compatibility have also been eliminated from the 360 APX.”

None of this, of course, will stop passionate outboard engine fans from dreaming. And there’s nothing wrong with that. Dream away.

Just don’t look for a consumer version of the 360 APX, much less the current version of the purpose-built outboard itself, to grace the transom of a pleasure boat anytime soon.

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