Boat Outboards 2013

By Michael Vatalaro
Published: April/May 2013

The past decade has seen an amazing array of changes and improvements in outboard engines. If you haven't shopped for one lately, you're in for a nice surprise.

Different Strokes For Different Folks

You'll notice all of these manufacturers are trying to design an outboard that "performs like a two-stroke," which is precisely the reason that two-strokes haven't gone away, just cleaned up their act. Direct injection (DI) is the innovation that allows a two-stroke to run cleanly and efficiently. By separating the fuel injection from the intake of air into the cylinder and, more importantly, waiting until the piston has risen far enough up the cylinder bore to block the exhaust port before injecting the gas, a DI two-stroke doesn't blow any unburned gas right through the cylinder and out the exhaust like its carbureted cousins. And because this process is electronically rather than mechanically timed, the engineers can tweak the performance with software rather than wrenches.

While Mercury offers Optimax DI two-strokes and Yamaha still has their "High Pressure Direct Injection" two-stroke engines in their lineups, Evinrude has chosen to offer only DI two-strokes, called E-TEC. Karl Sandstrom, product manager of Evinrude Outboards, says that using computers to control engine timing, and the smallest details of when and how combustion happens, allows them to adjust for maximum efficiency under different operating conditions. "Forty percent of an outboard's duty cycle is at or near idle speed, either trolling or motoring in no-wake zones," he says. "With the computer power we have, the engine can act like a very small outboard when all that power isn't needed, then switch to homogeneous mode when it is."

Photo of Mercury's Optimax engine
Mercury's Optimax engines are beloved by bass fishermen for their
quick throttle response and fuel-thrifty ways.

At idle, he says, the computer can tell the engine to inject only a tiny amount of gas, far less than needed to create a combustion event that would fill all the space above the piston, which is typical. Instead of a big bang, you get a little pop, enough to keep the piston moving (stratified combustion). But hit the throttle and the engine switches to homogeneous (all the same) mode, and enough fuel flows to make the combustion event fill the entire space. This fuel-saving strategy has even made its way into newer-model cars.

Meeting The Demands Of Modern Boaters

A cutaway illustration of Honda's BF250©2013 Mirto Art Studio,


A cutaway of Honda's BF250 shows a special air-intake design that allows a belt-driven fan at the front of the engine to take cooler out-side air and funnel it to the engine, generating more horsepower.

As the industry refines and improves outboard technology, they haven't ignored the changes in how boats are equipped and run. In particular, the demands put on a boat's electrical system have risen as more and more boaters equip their boats with large-screened multifunction displays and all the accompanying gizmos. Electronics manufacturers have built fancier and fancier equipment that sucks more and more juice to satisfy gadget-loving boaters, forcing outboard engine makers to find innovative ways to provide all that power.

First and foremost, outboards have become more energy efficient themselves. Using less electricity for internal operations means there's more left over to charge the battery and run your chartplotter, sounder, radar, stereo, iPod, VHF, AIS, night-vision camera, and so on. But even so, more powerful alternators are needed. Honda has created a system they call Amp+, which senses the electrical load on the battery and bumps up the idle speed of the engine if necessary. Yamaha started using those aforementioned rare-earth magnets that make 13-percent more power, but reduce the weight of the alternator by 10 percent. But perhaps the most far-reaching development, not directly related to the engine, is the rise of electronic engine controls, also called "fly-by-wire."

No More Cables

No matter what you call it, using electrons rather than a metal cable to change throttle positions, steer, and shift your outboard has numerous benefits. Chief among these is that it eliminates the burden of routing through the bowels of your boat one or more stiff, unforgiving mechanical controls that will eventually freeze up due to rust.

"You can tie 12 granny knots in a digital throttle and shift cable, and it will still work," says Mercury's Miller. But digital control means more than simpler rigging. All sorts of useful benefits, including automatic dual-engine synchronization, single-lever control options, steady-speed presets for towing skiers, and perhaps the most popular, joystick control, all derive from letting the computers talk to the outboards.

The digital link between throttle, shift, and steering controls spills over into the instruments and gauges as well. Gone is the need for four or more separate gauges on the dash to monitor critical outboard information. Single, wide-screen gauges with preset and programmable displays can show more and better information than an analog-gauge cluster. Today's display screens can also learn. "The Smartcraft gauge clusters don't just tell you how much fuel you're burning," says Miller. "It learns your boat. The gauge coaches you toward your fuel-efficiency sweet spots." It can even remember optimal trim settings.

The Coming Decade

As outboard manufacturers further refine their offerings, we'll continue to see improvements in performance, efficiency, and power output. Many in the industry expect the EPA to apply the same emissions standards to outboards in 2018 as they recently did to inboard engines, which would make a catalytic converter necessary. To accomplish this, manufacturers would have to switch to closed-loop cooling, like on an inboard engine. An engineering challenge to be sure, but Seven Marine, a newcomer to the outboard market which marinized a GM 8-cylinder engine, already offers closed-loop cooling on their 557-hp outboard and a horizontal engine orientation, both of which are unique in today's market. Given the remarkable changes in the past 10 years, those may not be unique attributes for long.End of story marker

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