After spending five years and $100 million Mercury Marine earlier this year unveiled its entry into the 4-stroke outboard market.
After spending five years and $100 million Mercury Marine earlier this year unveiled its entry into the 4-stroke outboard market.
The much-rumored “Project X” became a reality named Verado, available in 200-, 225-, 250- and 275-hp versions. What Mercury actually succeeded in doing with its time and money was to manufacture a 4-stroke outboard engine with completely integrated propulsion, steering and control systems, providing the end-user with performance, efficiency and quiet operation.
Mercury says it combined existing high-performance engine technology with specifically engineered systems and components to launch the first production outboard to feature a supercharger, which dramatically improves 4-stroke performance.
Mercury chose the Lysholm-type supercharger for Verado, which uses two twisted, counter-rotating rotors to force air through. It is similar in operation to the more common Roots-type supercharger but has a basic advantage. The Lysholm internally compresses the air as it passes through and gets forced into the intercooler, while the Roots only displaces the air column without the benefit of additional pressure.
The boost charge on Verado can reach a very efficient 15 psi, which is one reason Mercury says it chose the Lysholm. Co-developed by Mercury and IHI Turbo America, Verado’s supercharger incorporates Teflon-coated aluminum rotors that spin on stainless steel shafts mounted in an anodized aluminum housing. The supercharger is driven off the crankshaft by means of a serpentine Kevlar belt.
In order to understand how and why a supercharger is used to enhance engine performance, it is helpful to know the basics of the 4-stroke engine cycle. To keep things simple, consider a 4-stroke engine as giant air pump. The first stroke allows the piston to draw air and fuel in through the intake system while the piston is traveling to the lower portion of the cylinder. The returning piston then compresses the air while the valves are closed, and the spark ignites the air/fuel mixture. The resulting explosion forces the piston down, in what is referred to as the power stroke. Finally the piston once again comes up, forcing the spent gasses out of the exhaust valve.
Increasing the density of the air charge entering the combustion chamber can enhance performance, which is where the supercharger comes into play. The mechanically driven supercharger force-feeds the combustion chamber with a denser air/fuel mixture. The denser charge will increase dynamic cylinder pressure upon ignition, allowing the engine to produce additional power.
While the supercharger is providing maximum airflow, it is up to the electronic control module to monitor the engine’s vital signs through an array of sensors. The module will tailor such engine settings as supercharger boost (regulated a maximum of 15 psi), fuel flow through the sequential multiport injection system, and ignition timing to compensate for fuel quality, ambient temperature changes, coolant flow and altitude, according to Mercury. It will ensure maximum engine performance, fuel economy and emission compliance throughout the engine operating range.
The Verado is designed to turn between 5,800 and 6,400 rpm with correct propping. It is interesting to note that the electronic control module is the only component that is replaced or modified to alter the horsepower ratings on the different models, according to Steve Miller, Mercury Marine product manager for large 4-strokes. There are no modifications to displacement, compression ratio or cam timing with the different horsepower ratings.
All Verado outboards are rated to run on 87 octane fuel except the 275-hp model, which is tuned to burn premium 92 octane fuel only, as its ignition timing and boost are pushed to the maximum, according to Mercury.
As with most things, when it comes to engine performance enhancements there is no such thing as a free lunch. While the supercharger is compressing the air, heat is being created. To aid in producing the required cool, dense air charge, an intercooler is installed, which is the heart of Mercury’s “charge air cooling.” An intercooler is similar to an automotive radiator in that it provides a method of heat transfer from one medium to another without combining the two. In the case of Verado outboards, the intercooler is placed after the supercharger, allowing the compressed air to be cooled by the engine’s seawater cooling circuit.
Designed from scratch
There is much more to the Verado 4-stroke than supercharging alone can provide. Mercury started with a clean page when designing the outboards, and evaluated several base engine design configurations for compliance with its newly created NVH (noise, vibration and harshness) guidelines, according to Clay Gaillard, Mercury Marine communications manager. The configurations included a normally aspirated 90-degree V-8, a supercharged 60-degree V-6, an opposed 6-cylinder supercharged, narrow configuration supercharged V-6, and the eventual choice of the inline 6-cylinder platform.
In addition, considerations were given for dimensional characteristics, as Mercury says it wanted to retain the conventional 26-inch centerline for multiple-engine installations. The inline-6 was the strongest platform related to its NVH guidelines, and inherently provides higher torque ratings, according to the manufacturer.
Mercury says it chose a fundamentally different approach than its foreign competition in achieving the desired performance. While the Japanese high-horsepower 4-strokes are large displacement, normally aspirated V-6 configurations — Suzuki’s 250-hp 4-stroke has a displacement of 3.6 liters — the Verado is based on an inline-6 cylinder of 2.6-liter displacement (158.5 cubic inches) having a bore and stroke of 82 mm by 82 mm (3.23 inches by 3.23 inches).
To help guide and oversee the Verado project, which uses technology previously not found in outboard engines, Mercury brought in a German engineering team headed by Klaus Bruestle, known for developing the Porsche Formula One engine program and who headed up the team that designed the Porsche Cayenne V-8.
In the tradition of Porsche, Audi and BMW engines, the Verado powerhead consists of three major components — the cylinder head, engine block and bed plate — which are secured together with a series of long bolts, reducing the block’s ability to flex while evenly distributing heat and operational stresses. These three components are cast from aluminum and are products of Mercury’s lost foam casting process, a type of metal casting that uses foam patterns to produce molds for the castings.
LFC has significant cost and environmental advantages, as well as enabling metal casters to produce complex parts often not possible using other methods, according to Mercury. With castings produced using the LFC process, fewer machining operations are required, due to the lack of fins and parting lines. The process also allows for consolidating parts into one integral component with well-controlled dimensional accuracy.
The one-piece cylinder head features dual overhead cams with four valves per cylinder and an integral water-cooled manifold. The camshafts, incorporating 8-mm chain drives, consist of hollow shafts with sintered steel lobes. Sintered steel is made from steel powders that are axially compacted in a pressing tool, using virtually 100 percent of the raw material. The process enables large production runs of highly complex, ready to fit precision parts. As sintered steel parts have a porosity of 5 to 15 percent, they are lighter than conventional cast or forged parts of the same geometry. The porosity generally results in noise reduction and enhanced lubrication due to the pores near the surface serving as oil or lubricant depots.
The Verado outboards’ valve clearances are factory adjusted and should remain within tolerance for several thousand hours, says Miller. The intake valves are made of conventional high silicone-chrome steel alloy, while the exhaust valves are manufactured of Inconel, a nickel-chromium-iron alloy. When comparing the more common practice of manufacturing valves from titanium, Inconel is tougher to machine and slightly heavier but does not display the tendency to age harden, gall or work harden, as titanium will.
The Verado engine block uses gray iron cylinder liners having a 1.5-mm wall thickness that Miller says can be bored and honed for oversized pistons during a major overhaul. The engine uses cast pistons with individual oil galleries that aid in pulling heat away from the skirt for longer life and maximum horsepower. A reinforcing girdle provides additional security for the crankshaft main bearing journals, similar to Formula One engine design, according to Mercury.
Four-stroke engine design requires a pressurized lubrication system, and Mercury addressed the requirement by incorporating a separate oil module within the AMS (advanced midsection) cowling. The module consists of an oil tank, pump, filter, heat exchanger, thermostat, oil cooler and fluid separator.
Steering and trim
Verado outboards feature “electro-hydraulic power steering” that has a small, remotely mounted, electrically driven two-speed pump in addition to the helm pump and integral steering cylinder. Mercury says the system eliminates the undesirable steering torque and feedback without sacrificing the “feel” that is crucial for vessel control at high speeds. It also helps to eliminate some of the excessive external hose and rigging issues found with conventional outboards.
Mercury says its Verado power steering is the first outboard system of its type, and is similar to the new generation automotive systems found on today’s high-end cars, such as the Mini Cooper. Most current steering systems incorporate a small hydraulic pump in the helm, which creates hydraulic pressure when the wheel is turned. The pressure is transmitted to a cylinder mounted horizontally on the engine tilt tube, which directs the force through a steering rod and directly to the engine mounted tiller arm. The hydraulic cylinder and steering arm remain parallel with the vessel transom. Although hydraulically actuated, these systems don’t provide true power-assisted operation and, depending on the system, can require that up to 15 foot-pounds of force be applied at the wheel.
The Verado system uses a brushless DC motor to operate a gear pump mounted within the boat that provides constant fluid pressure to the engine-mounted steering cylinder, according to Mercury. There are no externally mounted steering rods or cylinders.
Turning the wheel opens an orifice at the helm, sending pressurized fluid to the steering cylinder for turning, while at the same time dampening engine torque feedback. The helm operation requires a constant 2.2 foot-pounds of input at the wheel under all conditions, including coming out of hard high-speed turns. The system will provide precise feel and control throughout the range, according to the manufacturer.
Mercury’s tilt and trim system uses its own motor and hydraulic pump housed inside the steering tube and packaged with the pedestal. As the integral system swivels with the engine, it is always in line with engine thrust loads.
The trim and tilt speed are governed by several operating conditions. When the engine is producing thrust, the trim rate will be slow, allowing the required precise adjustments to be made. The rate of speed will increase when there are no thrust loads, such as when docked or bringing the boat onto a trailer. The maximum angle of tilt and trim also can be set through a dealer programming of the SmartCraft computer or by using a hand-held diagnostic tool. This can help prevent dangerous overtrimming of the engine in addition to preventing the cowl from smashing into an obstruction on certain installations.
Mercury’s digital throttle and shift system controls are standard with the Verado outboards. The electronic control system communicates directly with the engine’s electronic control module to control engine speed and shifting. Gone are the days of mechanical shift and throttle cables that wear out, break and require constant maintenance.
Noise levels and gears
The AMS progressive rate mounting system reduces transmitted vibrations by 50 percent over a conventional engine mounting system, according to Mercury. It isolates the powerhead from other components by using a perimeter mounting system and rubber mounts that have the ability to vary their shock absorption characteristics based on applied load. The midsection also features a new heavy-duty bevel gear transmission with electronic shift system.
Mercury controls Verado’s sound level in a number of ways. A patented highly tuned intake resonator delivers a sound reduction of up to 14 decibels from midrange to full throttle without sacrificing engine performance, according to Mercury. The exhaust system incorporates a low-pass acoustic filter in the idle exhaust relief system, which Mercury says attenuates the high-frequency exhaust noises and makes Verado virtually silent at idle speeds. There is extensive use of acoustic foam in the top cowl and closed cell foam lining in the chaps, which absorbs high-frequency mechanical engine and drive shaft noise.
Verado’s new gear case is slightly larger in diameter and length than Mercury’s 3.0-liter unit in order to package the larger and stronger gears, reportedly 50 percent more durable than traditional gears. Redesigned stiffer prop shafts, stronger spline connections and a stronger gear housing round out the list of new hard parts.
Redesigned, higher temperature-capable seals are used throughout the gear case, as well. The dual water pickups help ensure adequate cooling water under all running conditions. The final drive ratio of Verado is 1.85-to-1, impressive in a 4-stroke outboard. Most normally aspirated 4-strokes are slower in developing torque at low engine rpm, so manufacturers typically attempt to compensate by lowering the gear ratio. With the intercooled supercharger of Verado, the extra horsepower and torque is available even at low and midrange rpm. Improved corrosion resistance is achieved through electro deposition painting of all internal water passages. Mercury offers the marine industry’s only three-year limited corrosion failure warranty according to Miller.
Verado is packaged with Mercury’s Engine Guardian System, an enhanced warning system designed to alert the operator of abnormalities associated with the engine temperature, voltage, oil or water pressure, and boost. The system will provide both audible and visual alarms through the SmartCraft system. In the event of an out-of-range alarm condition it will reduce engine throttle, bringing the engine back to a safe operating condition to minimize the potential impact.
The Verado is assembled and tested in a computer-controlled facility, where a complete engine buildup requires four hours from start to finish. The partially assembled engines go through a process known as IPV, or individual part validation, where each subassembly is confirmed to be within specification. If there are any deficiencies noted, Mercury says, the unit is removed from the line and returned to the responsible operator for correction. Following final assembly, each engine is cord spun to establish oil pressure, then started and run for 20 minutes, according to Mercury.
Verado outboards should be available this summer. Suggested retail pricing ranges from around $17,500 for the 200-hp Verado to around $20,400 for the 275, including the required rigging kit. For more information visit www.mercuryverado.com.
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Building a better 2-stroke
Bombardier Recreational Products’ new line of brawny 200-, 225- and 250-hp Evinrude E-TEC direct-injection outboards should be in dealerships by November, in time for the 2005 model year, says Karl Sandstrom, Bombardier product manager.
Like the two-cylinder 40- and 50-hp, and three-cylinder 75- and 90-hp E-TECs Bombardier introduced last fall, these six-cylinder 2-strokes are being touted as clean, light, efficient, low-maintenance, powerful and fully able to compete on all those scores with any of the 4-strokes on the market today.
While acknowledging that 4-strokes have the momentum in the outboard market, Roch Lambert, Bombardier executive vice president for sales, marketing and product development, believes this will change. “We’ve done our homework on this thing,” he says. “Five years from now this is going to be the technology.”
Bombardier says E-TEC outboards have a “stratified fuel combustion chamber” that delivers cleaner, more efficient fuel burns. Fuel reaches the exhaust port only after it has closed, in half the time of traditional direct-injection engines. This means the fuel charge doesn’t escape the combustion chamber, especially during idle, as it is burned and turned into power, says
The stratified combustion chamber also offers better fuel efficiency because of its precise fuel flow, according to Bombardier. The E-TEC system senses when to change the number of droplets going into the chamber, depending on engine needs.
Bombardier says all of the E-TEC outboards will carry the California Air Resources Board’s three-star, or ultra-low, emissions rating. This is one of the highest set by CARB, North America’s toughest emissions watchdog.
Sandstrom says a 225 E-TEC weighs in at a svelte 530 pounds (compared to 649 pounds for Mercury’s 225-hp Verado 4-stroke), produces noise levels around 84 decibels at the transom at 3,500 rpm, and burns 19.4 gallons per hour powering a 29-foot Triton 2895 — all good figures relative to 4-strokes. The big engines have been subjected to 15,000 hours of testing, the smaller ones 30,000 hours. After a year on the market in Australia and eight months in the United States, Bombardier has found “no issues” with reliability, Lambert says. While acknowledging only time will tell how durable the E-TECs are, Lambert says user experience to date “meets and exceeds” expectations.
Bombardier put a lot of thought into making the engines easy to own and maintain, which with durability and reliability are consumers’ biggest concerns when they buy an outboard, says Lambert. The E-TECs require no scheduled dealer maintenance for three years or 300 hours of normal recreational use. They need no break-in period and don’t have to be winterized or taken to a dealer for a spring tune-up. The computerized electronic engine management module does all that automatically, according to Bombardier.
The starting system is designed to fire up within one revolution, and all models have an emergency rope start in addition to the electronic ignition.
Sandstrom says the engines are more simply designed with fewer moving parts than 4-strokes and have no belts, powerhead gears, cams or mechanized oil pumps that can break down. He says Bombardier has designed the E-TECs to deliver a simple, no-hassle ownership experience.
“We have a hell of a mousetrap,” he says.
Bombardier has targeted several markets with the big-horsepower V-6 E-TECs. It will have a saltwater version of the 200, 225 and 250; a freshwater version targeted at pontoon, deck and aluminum fishing boat owners; and a high-output model of the 200 and 225 for tournament bass and walleye anglers. Still to come are 9.9-, 15-, 25-, 30-, 100-, 135-, 150- and 175-hp E-TECs. “It’s going to be a complete engine lineup,” says Sandstrom.
Despite Bombardier’s December sale to a group that includes the Bombardier family, Lambert says the E-TEC rollout is on schedule, with most of the line available by next summer, he says.
Evinrude’s sister company, Johnson — also owned by Bombardier — sells traditional carbureted 2-strokes and a line of Suzuki-built 4-strokes marketed under the Johnson name. Lambert says it will be up to consumers to choose which they like best, but Bombardier clearly has chosen its favorite.
“We believe in what E-TEC has to offer,” says Scott Croft, Bombardier manager for the big E-TEC outboards. “It does everything a 4-stroke can do and more. We believe it’s the technology of choice.”
For more information visit www.brp.com.
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A new 250-hp 4-stroke outboard with variable camshaft timing was the centerpiece of Yamaha’s midseason introduction of new and updated engines. The company also added electronic fuel injection to its family of 4-stroke outboards from 50 hp to 90 hp, and unveiled a new 200-hp 3.3-liter HPDI (high pressure direct injection) 2-stroke outboard.
The new F250 is the largest model in a 4-stroke line that includes two other V-6 outboards, the F200 and F225. Touted by Yamaha for use on offshore fishing boats, the F250 uses a 3.3-liter 24-valve dual overhead cam engine block.
Yamaha says its variable camshaft timing system is designed to increase low-end and midrange torque by advancing and retarding the intake camshafts to vary the intake timing. This is achieved hydraulically as the engine control module directs the oil control valve to supply oil pressure in the variable camshaft actuator to advance and retard camshaft timing based on engine rpm, according to the company.
The intake valves open and close sooner when the intake cam is fully advanced, placing the combustion chamber in valve overlap condition and increasing efficiency. This also helps build higher combustion chamber pressure, according to Yamaha.
Yamaha claims a 16-percent gain in torque in the 2,000 to 5,000 rpm range using the variable camshaft timing system. The system uses a new electronically controlled single throttle valve intake and a long intake manifold for increased performance and reduced noise, according to the company.
The 60-degree engine block uses Yamaha’s patented in-bank exhaust system, which reverses conventional 4-stroke intake and exhaust layouts to make the engine more compact and lightweight and increases performance, according to the company. The in-bank exhaust allows for long tube intake tracks that Yamaha says are tuned to increase air flow.
The F250 can use large-diameter intake and exhaust valves because the intake tracks are engineered to deliver air and fuel more directly to the combustion chamber, according to Yamaha.
The exhaust pressure reduction system comprises an air passageway in the lower unit that relieves exhaust pressure, which Yamaha says increases horsepower output. Since the F250 vents its exhaust through the propeller, the exhaust pressure reduction system also cools the propeller hub and increases prop durability, according to Yamaha.
Other key features include a single-belt drive system, a blow-by gas reburning system, a vapor gas reburning system, a high-output alternator, multiport fuel injection, and forged pistons.
The big 4-stroke has a three-star emissions, or ultra-low, rating from the California Air Resources Board and is EPA 2006 compliant, according to Yamaha. It is available with a 25- or 30-inch shaft and is backed by a three-year limited warranty.
Yamaha has added electronic fuel injection to its F50/F60 and F75/F90 4-stroke outboards, including the high-thrust T50 and T60, and the F60 and F90 Jetdrive models. The multiport fuel injection system is controlled by the engine control module and uses four independent fuel injectors located just above the intake valves to deliver the precise amount of fuel to each cylinder, according to Yamaha.
All these models also will be outfitted with Yamaha’s new variable trolling system, which allows the skipper to increase or reduce engine-trolling speeds in 50-rpm increments by using a tiller-mounted switch. In addition, the F50 and T50 outboards now will be based on the same 1-liter engine block used by the F60, and the F90 will be available with a 25-inch shaft.
The new 3.3-liter VZ200 joins Yamaha’s VMAX line of high-performance freshwater 2-stroke outboards from 150 to 300 hp. The 200-hp engine features a 76-degree V-6 engine block and the HPDI system, which delivers fuel at 1,000 psi using two high-pressure fuel pumps for more complete combustion.
Yamaha says it has made an allowance for the VZ200 to be used on bay boats and bass boats by adding larger engine anodes inside the cooling passages to help prevent corrosion. The use of YDC30 aluminum alloy and a freshwater flushing system should also help in this area.
The VZ200 is available only with a 20-inch shaft and carries a two-year limited warranty.
For more information visit www.yamaha-motor.com.