The New Outboard Engines

by Alex Zidock Jr.

There is a wide choice of very good outboard motors available for Pennsylvania boaters. Today's modern engines are packed with technology that has been developed in the last five years. Engine manufacturers forced their research and development teams to come up with engines that meet the United States Environmental Protection Agency's (USEPA) proposed emissions standards. In addition, manufacturers have leveled the playing field by introducing better warranties and offering more inclusive, extended-service programs.

One of the most important choices purchasers of new outboard engines have today is whether to go with the enhanced versions of the old two-stroke engines or with the popular four-stroke models. Two-stroke engines are those in which the gas and oil are mixed either by the operator before the fuel is added to the gas tank or by a direct injection process where oil is held in a separate reservoir. The gas/oil mix lubricates the working parts of the engine.

Four-stroke engines are like automotive engines. The gas and oil never mix, except by accident or malfunction. In fact, one outboard engine manufacturer's newest model has the same pistons, rods and crankshaft as one of the company's automobile engines. The block is different to meet outboard design specifications. It used to be that the four-cycle engines burned much cleaner than their two-cycle cousins, but modern technology such as direct fuel injection, electronic fuel injection and digital fuel injection have cleaned up the two-stroke's act.


Honda Marine has never built anything except four-stroke engines. So it's no surprise that all of its 2000-year model outboard motors are four-strokes with a 130 hp at the top of the list. The biggest problem four-stroke engines had to overcome over the years was their weight-to-horsepower ratio. Traditionally, the four-strokes are heavier than their two-stroke cousins of the same horsepower. But if your boat can handle the weight, what you gain is a quiet, smooth and environmentally friendly outboard that meets or exceeds the 2006 federal emissions requirements.


OMC (Outboard Marine Corporation) offers a full lineup of two-stroke and four-stroke engines under the Johnson and Evinrude banners. According to OMC, the new Ficht(tm) Ram Injection technology has revolutionized direct fuel injection (DFI). "Ficht" is the name of the company that developed this new technology, which OMC bought. Direct fuel injection, the engineers say, has an advantage over older carbureted two-stroke engines because the newer DFIs produce over 80 percent less hydrocarbon emissions and offer improved fuel economy. They use up to 50 percent less lubricating oil, run smoother and practically eliminate exhaust smoke. Marketed under the Evinrude brand will be a new 25 hp four-stroke engine that will join other four-stroke engines in the 4 hp to 50 hp class.


Mercury Marine is offering Digital OptiMax outboard motors, which are now compatible with their new SmartCare system. Some long-shaft configurations for offshore V-6 use have been added as well as new 6, 75 and 90 hp four-stroke models. A 40 hp model has also been added to satisfy the needs of pontoon boat owners. The engine features an oversized heavy duty gear case. This allows for the use of a larger propeller that provides higher thrust for increased maneuverability, holding and stopping power for heavier craft.

OptiMax DFI two-stroke technology, which has been around for a couple of years, and now the Digital OptiMax, allows these engines to communicate with the Mercury SmartCare system. This system consists of two advanced gauges (Smart Tach and Smart Speed), which provide engine, boat and environmental information that used to require up to seven gauges, as well as advanced engine monitoring and control.


New this year for Nissan/Tohatsu will be 4 hp, 9.9 hp and 15 hp four-stroke engines. A 50 hp direct-injection outboard engine will be introduced later in the year, and a 90 hp direct-injection model is scheduled for introduction in the model year 2001.

Tohatsu Corporation manufactures outboard motors for Nissan Marine ranging from 2.5 hp to 140 hp; this is the only relationship between the companies.


Suzuki Marine has introduced two new four-stroke models for 2000. The 25 and 30 hp offer a newly designed three-cylinder, single-overhead-cam powerhead. Two intake valves and a single exhaust valve for each cylinder increase horsepower and torque. These four-strokes include a chain-driven valve train with hydraulic adjuster that has proven to provide reliability and durability in other Suzuki models. Among other features you'll find on the tiller models is a front-mounted linear steering adjuster that lets the operator tighten or loosen steering movement without tools. If you prefer two-stroke motors, Suzuki has engines from 5 hp to its V-6 225, which meet or exceed the EPA 2006 emissions requirements.


Yamaha has introduced High Pressure Direct Injection (HPDI) two-stroke outboards for 2000. HPDI is featured on seven all-new motors in 150 and 200 hp ratings, including counter-rotating versions for dual installations.

To understand Yamaha's take on its system, you have to understand that conventional two-stroke carbureted engines deliver the fuel/oil mixture up from the bottom of the cylinder. The exhaust port is partially open as the piston moves up, compressing the fuel/oil charge. This mixture then goes up and around the piston to get to the top of the cylinder head for combustion. Some of the mixture escapes through the partially open exhaust port. The spark plug can fire only after the piston completely covers the exhaust port. Yamaha engineers say that as a result of this process, some fuel efficiency is lost.

In direct injection engines, the oil still comes in from the bottom of the piston, but the fuel is delivered by way of the fuel rail and injectors from the top of the piston under pressure from 90 to 250 psi. The engine is designed to wait until the exhaust port is closed before firing. The precise amount of fuel can be delivered at the right time. The big difference in Yamaha's HPDI system is that the fuel is pressurized to 700 psi, before atomizing, which Yamaha says allows for a more complete burn.

Yamaha has added a new 115 hp to its four-stroke lineup featuring an in-line four-cylinder with multi-port fuel injection, dual overhead cams, four-valve long-track induction system with silencer, and front air intake.

Yamaha offers models from 2 hp to a 3.1-liter fuel-injected 250 hp engine.

With all of the variations of direct injection technology applied to two-stroke engines, and with the improvements made to four-stroke engines, modern outboard motor manufacturers have a lot to offer boaters over the outboard engines of just a few years ago. Older engines smoked and dumped oil into the water and hydrocarbons into the air through exhausts that contained unburned fuel and oil. With USEPA emissions restrictions getting stricter, both the environment and outboard users will benefit. Newer outboard engines burn fuel a lot cleaner, they are a lot quieter and easier to start, and they're more reliable and more fuel-efficient. Even though the selection of outboard motors in the marketplace has grown, the difference between what was available just five years ago and what's available today is amazing.

March/April 2000 Angler & Boater

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