Today's larger outboard engines look vaguely like those produced 30 years ago, and both early and late models run by internal combustion. However, the similarities pretty much end there. Remember when "loop charging" seemed like a big deal? It was at the time. But overall, technological advancements came slowly over several decades, and it wasn't until the 1980s that things began changing rapidly.
That's when Yamaha joined the U.S. market. Just as Japanese cars had done a decade earlier in the automotive industry, Japanese outboards set a new standard for quality, and things haven't been the same since. American outboard manufacturers suddenly had to compete with foreign products that the public immediately embraced, setting off a mad scramble for market share that continues to this day.
In the early days, competition between American outboard companies revolved around who made the biggest engine with the most horsepower, but the Japanese shifted the focus to technology and reliability issues, as well as things like standard versus optional equipment. You may recall that Yamaha scored big points in the '80s by including a propeller as standard equipment. This sometimes-fierce competition eventually claimed several American casualties, including Chrysler Marine and, ultimately, one of the biggest names in the business, the Outboard Marine Corporation, builders of the venerable Johnson and Evinrude brands (now owned by the Canadian firm, Bombardier Recreational Products).
Technological advancements in higher-horsepower engines came faster and faster in the late '80s and '90s in the form of fuel injection, oxygen sensors, tuned exhausts and fuel induction, as well as greatly improved two-stroke oils, which extended service life. Many of these appeared as the result of efforts to simply improve reliability and fuel economy, but then the Environmental Protection Agency stepped in, and the game changed once more.
The EPA developed stringent new emissions guidelines in the '90s. Many of them were adaptations of the extremely conservative emissions standards developed by the California Air Resources Board (CARB), among the toughest air-quality standards in the world. This brought about the race toward four-stroke technology, which has some inherent advantages over conventional two-strokes in the emissions department. But the two-stroke believers countered by developing ultraclean and efficient two-stroke, direct-injection models of their own. And of course some companies hedged their bets by pursuing both two- and four-stroke development on parallel courses.
In those few years since the late '90s, technology has accelerated at a dizzying pace, with new developments coming at us with every model year. Computers now control much of what goes on beneath the cowlings of high-horsepower outboard engines, allowing much more control over the fuel-burn process. The EPA and CARB mainly measure and regulate pollutants such as hydrocarbons (HC) and nitrous oxides (NOx). These agencies also measure, but do not regulate, carbon monoxide (CO) emissions.
Hydrocarbons are just unburned fuel, and computer-controlled, high-pressure fuel injection enabled manufacturers to eliminate a very high percentage of the HC emissions in two-strokes. High-pressure fuel pumps deliver gasoline to the cylinders as a very fine, atomized spray, and computers control the timing of the injection and the spark so that very little fuel passes through the cylinder unburned. The outboards of my youth belched blue smoke and left a rainbow-colored sheen on the water wherever you went. But technology has eliminated such obvious pollution, and today's outboards run much cleaner and more efficiently.
Likewise, four-strokes use computer-controlled fuel injection to greatly reduce emissions of hydrocarbons, albeit at a substantially lower pressure. And because four-strokes don't burn oil in the combustion process, their NOx emissions theoretically run lower than those of two-strokes. Obviously, manufacturers have designed the latest two- and four-stroke power to meet the latest round of EPA standards, which take effect this year, offering the public many choices.
Both technologies offer distinct advantages. Two-strokes produce a lot of power from a relatively light block, although direct injection has added weight to the design. The throttle response of a two-stroke makes it attractive to a great many of us who desire that familiar outboard "punch," with instant acceleration and a neck-snapping hole shot. They simply perform like the outboards we've been used to over the years. Four-strokes lacked some of that low-end acceleration in the beginning, but at the same time they offered much quieter and smoother operation. When the big four-strokes hit the market, people would invariably walk up to you at the dock as your boat idled and say, "Is that thing running?"