Four decades after mandating the first pollution controls on automobiles, Environmental Protection Agency (EPA) regulators have finally gotten around to outboard motors. The big hit comes in a few years with the EPA 2006 standard. EPA 2006 mandates a 75 percent reduction in emissions, which essentially means that conventional two-stroke outboards can no longer be sold. Manufacturers are scrambling to develop clean-burning engines that meet the impending rules.
Unlike modern automobiles, which all use similar four-stroke, EFI technology, outboard motors employ new ideas. However, there are strong advantages and disadvantages to each technology—differences that are hard to sort out without head-to-head testing.
Which is where we come in. We invited representatives of all five major outboard motor manufacturers to join us for five days of back-to-back testing at Lake Lanier, northeast of Atlanta, Ga. The only point at which all the new technologies intersect is 115 hp, so that’s the engine size we tested. Each manufacturer’s engineers had a whole day to rig and test their motor, trying different props and mounting positions until they were satisfied this was the best their engine could do on that hull on that water on that day.
The factory engineers selected very different propellers, trying to match the characteristics of their motors to our hull. After trying three-blade props, the engineers from Honda and Mercury opted to use four-blade props, which seemed to give quicker acceleration and noticeably better bite in high-speed corners. The other manufacturers stuck with their three-blade props, though in dramatically varied diameters and pitches. Part art and part science, propping a boat and motor into a perfect system is just as important as picking the right set of tires for a NASCAR race car.
Our test results are fascinating. Compared to the blue smoke generators of even two years ago, all these 2000 model outboards are the very models of decorum. Thanks to computerized fuel injection, they start and run without a hiccup from idle to WOT. All the outboards in this group except for the EFI Suzuki two-stroke already meet the EPA 2006 standard. Today’s four-stroke outboards are significantly quieter and more economical to run than today’s two-strokes, but are also physically larger and slower to accelerate.
How We Tested
All tests were performed with only a helmsman and test equipment operator aboard, plus 15 pounds of test equipment and 10 gal. of fuel. All tests were performed several times over an identical course to ensure accuracy and repeatability.
Sound level readings were taken with an Extech 407735 sound level meter reading on the A scale, with the sensor located behind the helmsman to reduce wind and hull noise. Fuel flow readings were taken with a FlowScan 5900 flow meter. Speed and acceleration readings were measured with a Stalker Sports Radar, calibrated before each run.
All motors were tested on consecutive days in a sheltered cove at the southeast end of Lake Lanier, near Lanier Islands. Prevailing test conditions: 60 to 70 degrees F, 60 to 70 percent humidity, wind at 3 to 5 knots and negligible chop.
Thanks to R&G Marine and Lanier Harbor Marina, both in Buford, Ga.
Honda’s best-selling Accord sedan has an enviable reputation for refinement and reliability. To create an EPA 2006-compliant outboard, Honda engineers cleverly adapted the 2.3-liter four-cylinder from the Accord.
The Accord’s 2.3-liter is rated at either 135 hp or 150 hp. The outboard is rated at either 115 hp or 130 hp when fitted with a restricted intake manifold that cuts top-end horsepower. This means that the 115 and 130 outboards perform similarly across most of the powerband.
The Honda four-stroke weighs 496 pounds, more than any other 115, which could be more of a factor on a lighter, shorter hull than our test Kenner. On the other hand, the Honda outboard is significantly quieter than its competition, significantly more economical on fuel and, thanks to its long-stroke design, it has a fat midrange torque curve that makes it easy to tow a skier or push a heavy boat.
Yamaha offers both a 115-hp two-stroke V4 and a brand-new 115-hp four-stroke inline Four that’s EPA 2006 compliant. Yamaha elected to bring the new four-stroke to this test. Compared to the Honda four-stroke, the 407-pound Yamaha is significantly lighter and more compact. It’s a 1.74-liter Four derived from the existing 1.6-liter F100, but it’s equipped with computerized multiport fuel injection and a separate throttle valve for each intake runner. This is a very sophisticated engine, complete with double overhead camshafts and four valves per cylinder.
Out on the lake, the Yamaha was a hairsbreadth slower in acceleration than the Honda, a decibel or two noisier, 0.6 mph faster and sipped virtually the same amount of fuel. It also costs $1370 less. In other words, pretty much identical.
Mercury’s 115 Optimax two-stroke is literally identical to the Optimax 135 and 150, save for a restrictor ring in the intake manifold and reprogrammed engine-control computer. Our test 115 certainly wasn’t hurting for power. It significantly outperformed the other 115 outboards at all speeds, while burning about 22 percent more gasoline than the four-strokes at wide-open throttle. Furthermore, it was the noisiest engine at high speeds.
The 115 performed like a big motor because it is. At 442 pounds, the 2.5-liter V6 weighs more than the Yamaha four-stroke. Plus, there’s a sizable tank of oil that must be accommodated. Lift the engine cowl, and the Optimax seems to have more add-on bits and pieces than the Yamaha or Honda, which means more potential trouble spots.
Optimax is Mercury’s name for a DFI system that injects the fuel under about 90 psi of pressure. The theory is that delivering pressurized, more finely atomized fuel into the cylinders results in a cleaner burn for more power.
It certainly seems to work. During our testing, not only was Mercury’s Optimax the best-performing 115, it went from prolonged idle to full throttle without a stumble or hint of oil smoke. That’s impressive for a big, six-cylinder two-stroke.
If Mercury’s 115 is a detuned 135, you can think of Evinrude’s two-stroke 115 as a hot-rodded 90. It’s a 1.7-liter, short-stroke V4 that likes to rev. At 349 pounds plus a small external oil tank, it weighs nearly 150 pounds less than Honda’s 115. Dale Kenner sells a boat similar to ours with twin Evinrude 115s, capable of over 70 mph. He can do that because two Evinrudes weigh only 200 pounds more than one Honda.
Evinrude uses a DFI system called Ficht, which atomizes fuel under pressure and squirts it directly into each cylinder at up to 450 psi. As with Mercury’s Optimax, the result is a clean-running two-stroke with no visible smoke and no plug fouling even at prolonged idle.
In our tests, the Evinrude was the second-quickest in acceleration behind the big Mercury, but slowest in top speed. Remember, even though all these engines are rated at 115 hp, the Evinrude is only a 1.7-liter V4 trying to compete with Mercury’s 2.5-liter V6. That’s tough. The smaller Evinrude used significantly less fuel than the Mercury at midrange cruise, but consumed the same amount at full throttle. It’s obviously working harder at high speeds.
Within a few months, Suzuki will introduce an EPA 2006-compliant four-stroke 115, but for our test, the company elected to go with its EFI two-stroke that will continue in production for the next few years. Compared to the Mercury and Evinrude DFI two-strokes, the Suzuki is similar in performance and noise. It’s a detuned version of Suzuki’s 140-hp outboard, but it weighs only 21 pounds more than the lightweight Evinrude. So it’s a very compact and efficient package.
The Suzuki is a very straightforward outboard: a 1.77-liter two-stroke inline Four equipped with automotive-style digital multipoint sequential electronic fuel injection, a secondary recirculation system to scavenge unburned two-stroke oil and an integral 6-quart oil tank hidden under the engine cowling that eliminates the messy separate oil tank still used by Mercury and OMC. Unlike the others, Suzuki’s 115 comes complete with your choice of stainless steel prop.
Where the Suzuki falls down is in fuel consumption. At 3500-rpm cruise, it burns more than twice as much gas as the Evinrude.
What Did We Learn?
The least expensive motor in this group is the Suzuki, which has an MSRP of $8934 and can be bought “on the street” for considerably less. On the other hand, it will also be the most expensive engine to run, having both the worst fuel economy and two-stroke oil injection. Suzuki’s new four-stroke will correct these faults, but will likely cost more.
The most expensive motor in this group is the Honda at $10,870 (MSRP), though it, too, can be purchased for considerably less. The Honda and similar Yamaha should be the least expensive engines to run, since they consume the least amounts of fuel and oil and should be virtually maintenance-free. They’re also the quietest, which we think is a big plus.
The Mercury and Evinrude DFI two-strokes are priced in the middle, offer the greatest number of dealers, reasonable fuel economy and the quickest acceleration. The Evinrude, in particular, is significantly lighter than other 115 outboards, which makes it perfect for smaller hulls or twin installations.
All five outboards were noticeably better than conventional two-stroke outboards—quieter, smoother, more powerful and more economical. All five seem impressively well-finished, with gleaming clearcoat paints and corrosion-resistant parts throughout. Which motor you choose depends primarily on the size and weight of your hull, which performance characteristics are most important to you and, truthfully, the best local dealer.
The Boat: Kenner 21 V-150
We needed a test hull that was perfectly balanced, easy to rig, easy to handle, quick to plane, fast, adaptable to five different engines with shaft lengths of either 20 or 25 in., had lots of room for test gear and, last but not least, looked pretty in our photos!
Everyone we talked to suggested Kenner Boats, County Rd. 63 E., Knoxville, AR 72845; 501-885-3171; www.kennerboats.com. Cousins Bill and Dale Kenner enthusiastically agreed to make a stripped version of their center-console 21 V-150, 21 ft. 7 in. long, with a 91-in. beam and 16 degrees transom. It’s hand-laid fiberglass, 100 percent foam-filled and covered by a five-year warranty.
This particular hull has the transom cut down to 23 in. and is equipped with an aircraft aluminum CMC Power Lift rated for 300 hp. This allowed us to test engines with either a 20- or 25-in. shaft.
For this test, Dale replaced the usual 36-gal. tank with a 15-gal. tank and left off most of the extras. What remains are a center console with 15-in. stainless steel wheel and live bait well, a 94-quart ice chest/helm seat with flip-back cushion, a forward storage locker and lots of deck space. The boat came out at 1209 pounds, ready to run.
Dale also made five identical consoles, each one prerigged with the instruments and throttle for one of the five test outboards. This saved us literally days when switching from one outboard to another. Two men could switch consoles in minutes, ready for the next test motor. Really, really slick. Like our Kenner.