Last year, Yamaha Outboards introduced a line of High Pressure Direct Injection (HPDI) outboards as part of its largest commitment ever in bringing the best in outboard motors to anglers and boaters. The HPDI system won three industry innovation awards in 2000 – the IMTEC Innovation Award, given by the National Marine Manufacturers Assn.; Motor Boating & Sailing magazine’s Innovation Award; and the Design & Engineering Award 2000 from Popular Mechanics magazine. For 2001, Yamaha is expanding that line with three new models – a premium175, a VMAX 175 and a VMAX 200. These engines meet the Federal 2006 guidelines today.
“Last year we introduced a 150 and 200 hp model for fresh and salt water use and a VMAX 150 for bass and flats boats- all with HPDI,” said David Grigsby, product manager of Yamaha’s Marine Power Division. “This year, we’re meeting the needs of more customers by filling some gaps in the horsepower line-up. Now anglers can get a 175 hp 25″ shaft outboard with HPDI for their mid-sized boats while bass, inshore and flats anglers can power their larger bass boats with HPDI’s fuel-efficient power.”
The Z175 HPDI outboard features a 25″ shaft while the two VMAX engines each have a 20″ shaft.
How HPDI Works
On conventional two-stroke outboards, the fuel/oil mixture enters from the bottom of the cylinder and must travel up around the piston into the combustion chamber. The exhaust port is exposed and open as the piston is in the down position. As the piston moves up and compresses the mixture, some of the fuel/oil mixture escapes out of the exhaust port. Once the piston blocks the exhaust port and the mixture is compressed, the spark plug fires and the mixture is ignited forcing the piston down. On Yamaha’s HPDI direct injection system, the fuel is injected from the top of the cylinder milliseconds before the piston reaches the top of its stroke. This precise timing allows for the exhaust port to be almost completely closed without permitting any unburned fuel to escape. This alone provides for greater fuel economy.
Adding to the when and where the fuel is delivered, an important element is how it is delivered. Yamaha developed a high-pressure delivery system that builds delivery pressure to 700 psi. Other systems utilize pressures ranging from 90 to 450 psi. This highly pressurized fuel means a more uniform atomization that results in a cleaner, more complete burn.
Another innovation of Yamaha’s HPDI is the injector. Competitors utilize an injector that protrudes into the combustion chamber creating a disturbance in the flow of fuel and leaves the injector tip susceptible to carbon buildup. Yamaha’s injector opens internally and does not protrude into the combustion chamber, and due to its internally opening design,ya developed a high-werhead and is not subjected to excessive heat exposure and carbon buildup. All of this means that an HPDI engine is a cleaner running, more fuel efficient and more durable outboard.
In addition, Yamaha uses a patented O2 Sensor to enhance performance by continually monitoring oxygen density in the exhaust gas and then instantly feeding the information to the microcomputer which then adjusts the amount of fuel that each individual fuel injector delivers. This means the right amount of fuel is always delivered, resulting in optimum power and fuel economy as well as improved durability and reliability.
Grigsby added, “The new 76-degree engine block that Yamaha uses on the HPDI motors provides more torque than 60-degree blocks and a more streamlined appearance over 90-degree designs. In addition, narrower engine blocks take up less space along the transom. This is important on twin-engine offshore setups when fighting a big gamefish requires all the maneuvering room you can get. A more streamlined cowl also offers less wind resistance for tournament or pleasure anglers who need to get to the hot fishing spots in a hurry.”
All three models feature Precision Blend Oil Injection which automatically injects the proper amount of oil depending on the needs of the engine. Engines running at idle need less oil than engines running at full throttle. The Precision Blend system measures RPM and throttle position to determine how much oil is needed.
Internal lubrication can also be a problem with conventional direct injection systems but not with Yamaha’s HPDI. On conventional direct injection systems, since the fuel isn’t mixed with the oil, an inadequate amount of oil flows past the bottom piston ring in each cylinder to adequately lubricate the top piston rings. This results in excessive heat and can damage the ring seal causing further engine damage. Yamaha’s HPDI system allows the upper ring to be lubricated by designing the bottom ring with 12 tapers or by-passes that allow the precise amount of oil to flow past the lower ring to the top ring. This translates into longer engine life and added durability for the consumer.
The HPDI motors feature a wide-range power trim and tilt that goes from -4 degrees for quick hole shots to +16 degrees to improve top-end performance. The motors can also be raised and lowered while the boat is on the trailer with the conveniently located pan-mounted tilt switch.
PrimeStart Auto Choke provides the proper fuel mixture for most weather conditions so that the motor starts quickly the first time the key is turned on. In addition, Yamaha’s HPDI motors use a pressure sensor inside the high-speed fuel pump that senses fuel pressure at startup and instantly relays that information to the microcomputer. The microcomputer then increases the duration that each fuel injector is open to enrich the fuel mixture for immediate starting instead of having the engine crank while building pressure and draining battery power as on conventional direct injection designs.
The HPDI motors feature a microcomputer ignition coupled with a throttle position sensor to provide better throttle response, timing control and engine protection without the use of a moving base plate under the flywheel. All this translates into optimum engine performance and better fuel economy. Overheat, low oil and over-rev sensors protect the owner’s investment in the engine and provide peace of mind. If a problem should occur such as debris in the water blocking the water intakes, the sensors alert the operator with a buzzer and warning light and automatically reduce engine speed to 2,000 RPM to keep the outboard from overheating and being damaged.
Alternator output of 30 amps at 1,000 RPM and 45 amps at 6,000 RPM keeps the batteries charged while allowing electronics or livewell pumps to run all day. A high-performance 1.86-to-1 gear ratio enables longer runs while using less fuel so far off fishing grounds seem closer or large lakes seem smaller.
Another strength of the new Yamaha outboards is their level of proven corrosion fighting measures. A front-mounted freshwater flushing device offers convenient engine flushing from the dock or the boat by attaching to a standard garden hose without any special tools. The motor does not need to be running to flush the engine. Protection from the elements comes from the ACP-221 paint application, a technologically advanced process featuring multiple layers of tough primer,
color and finish coats. Stainless steel components battle internal corrosion while all aluminum components that contact the water are made from Yamaha’s tough YDC 30 aluminum alloy. Zinc anodes in the powerhead, the lower unit and on the power trim and tilt bracket sacrifice themselves to protect other metal components from corrosion.
The Yamaha key switch features a standard engine stop switch lanyard that conveniently clips to the operator’s wrist, clothing or personal flotation device which automatically stops the engine if the operator leaves the helm.
Like all Yamaha two-stroke outboards, the new motors are backed by Yamaha’s Two-Year Factory Limited Warranty at no extra cost.
For the location of your nearest Yamaha Outboard dealer, call toll-free (800) 88-YAMAHA.
