Speaking of triple and quad installations, where will that end? We've seen bigger and bigger boats come to the market with outboards, boats that would traditionally have had inboard power. Is there an upper limit to possible outboard horsepower, and if so what is it? It depends on whom you ask.
"Outboard manufacturers must think of ways to use existing platforms to steadily increase power," says Bruestle. "It would be nice to provide 800 to 1,000 hp for these larger boats with twin engines rather than triples or quads, because the drag is 30 to 40 percent lower when you go from quads to twins." A 500-hp outboard? It could come sooner than you think.
The concept of using existing platforms is important, because bringing designed-from-scratch new engines through the exhaustive R-and-D process all the way to the market costs millions of dollars, but the outboard industry simply doesn't generate enough capital to make it worthwhile in most cases. Worldwide, consumers buy slightly fewer than 700,000 outboards annually, making it very difficult to justify spending that kind of money to develop totally new products.
If you develop a successful new automobile, you can spread that cost over millions of unit sales, but the smaller numbers in the outboard market hamper development somewhat. Being in the automotive business as well gives Yamaha, Honda and Suzuki some advantage in developing new technology of course. But because of the prohibitive costs of developing engines strictly for the marine market, don't expect to see all-new technologies like high-tech diesel outboards or rotary engines anytime soon.
Some outboard industry observers believe that as outboard-powered boats get larger and horsepower ratings increase, new lower units with larger-diameter propellers will be needed to efficiently push all that mass, especially in rough water where it's necessary to push tons of fiberglass uphill from time to time. Even the largest outboards still swing props with only about 16 inches of diameter, and one advantage of triples or quads is that you get that much more blade surface in the water to shoulder the load.
"I definitely think we'll be seeing outboards in the 400-plus-hp range sometime soon," says Senger. "The key to high-horsepower outboards is gear-case durability. Look for sterndrive-type lower units with straight-cut gears, transmissions and torque converters under the power heads."
"As power levels increase, so does the need to convert that power into useful movement through the water," adds Meeler. "While that doesn't necessarily mean bigger lower units in terms of size, the strength required to handle that power must increase. Additionally, any changes in hydrodynamics based on increased engine power will require propellers designed accordingly."
Bruestle also sees the possibility of marine transmissions somewhere down the road. "A two-speed transmission would be perfect for heavier boats," he says. "Or you could incorporate as many as three gearing levels. You would need a clever system totally controlled by the engine's microprocessor, which would recognize how you are driving and maintain the correct engine speed. You always want the lowest possible engine speed with the throttle as open as possible."
A marine transmission would start with a lower gear for quick acceleration, then shift to a slightly higher gear ratio as the boat climbed on plane. When it reached full cruising speed, it could even drop down into a final overdrive gear to enhance speed versus rpm and therefore enhance fuel economy.
Given the outboard industry's ongoing quest for additional horsepower, it seems logical that we might see more turbo-charging and supercharging in the future, but our experts split over that question. Mercury has obviously embraced the technology, but others don't harbor the same confidence in it. "I don't see a lot of supercharging in future outboards," says Greenwood, "unless the cost of manufacturing comes way down. The only advantage it offers is to help an engine with a too-small displacement make horsepower."
"Supercharging and turbocharging are primarily unproven in the marine outboard engines," says Meeler. "The drawbacks to that technology include increased heat under the cowling, weight, increased fuel consumption and stress on the engine's internal parts." Senger disagrees, however. "Supercharging is a proven technology, which creates concerns about heat buildup," he says. "This normally means more fuel is needed to help cool the engine. However, with intercoolers and closed cooling systems, we can easily overcome those concerns."
We've discussed larger-horsepower outboards exclusively because that's where technologies change most rapidly, but smaller outboards have undergone substantial changes, too. Although two-stroke models exist, the trend is undoubtedly toward four-stroke technology in the lower-horsepower ranges, once again with the notable exception of Evinrude's E-TECs. That's important because the average-sized outboard sold in the United States is still only around 90 hp, but the high-tech advances are beginning to trickle down to the smaller engines.
More changes will undoubtedly come, because new and more stringent emissions mandates loom on the horizon. The next EPA-mandated change occurs in 2012, and although it has yet to set a clear reduction goal, CARB is already considering lowering the acceptable emissions of HC and NOx from 16 grams per kilowatt hour (what went into effect this year and has been met by all outboard engine manufacturers), to 5 g/kw hour, and the EPA often follows CARB's lead. It's unclear whether two-strokes could meet such a standard at all. Four-strokes would have to add catalytic converters, which would create a lot more complexity and add a lot of cost to each engine. "We just hope they go after all the lawn mowers out there before they come after us," jokes Bruestle.
Time will tell. In the meantime, we all benefit from a wide selection of excellent choices in outboard power. The engines of today definitely aren't your Uncle Bob's old fishing kicker; they're much better, with high-tech features and levels of reliability and economy unheard of until very recently. And they will only improve with time.