The conventional two-stroke outboard motor has been an essential and prized possession of fishermen and recreational boaters for nearly 75 years. Although smelly and loud, they have been engrained in the American summer culture. Their sound brings back a flood of memories filled with fishing trips and lazy summer afternoons on the lake.

However, changes in the outboard market are on the horizon. Like their counterparts in the motorcycle and snowmobile markets, traditional two-stroke outboard motors are being replaced by cleaner four stroke engines and direct fuel injected two stroke engines. The change is being driven by the Environmental Protection Agency (EPA), which is mandating a 75 percent reduction in outboard hydrocarbon and NOx emissions by 2006. That standard has already been implemented in California, with tougher ones on tap for 2008.

Similar to emissions limits imposed in the auto industry, outboard emissions limits do not apply to single engines. According to Don Schultz, chairman of the National Marine Manufacturers Association (NMMA) Oil Certification Committee, the reductions apply "across a company's whole engine line, and all engines in the aggregate must meet the standards."

Since emissions limits don't take effect until 2006, the conventional two stroke motor isn't likely to become a dinosaur anytime in the near future. After all, conventional two strokes still outsell four stroke and direct fuel injected two stroke outboard motors by a wide margin, and a well maintained two stroke outboard motor can literally last for decades.

The NMMA, responsible for setting specifications for marine motor oils, has indicated that wear protection is a top priority in setting specifications for the new breed of outboard motors. Oil for two stroke direct injection motors will continue to be licensed through NMMA's TC-W3 program, while a new program (most likely FC-W) will be created for the licensing of oil for four-stroke motors. In both programs, the "W" stands for "water."

Conventional two stroke engines have traditionally relied on the carburetor to feed an air and gas mixture into the combustion chamber, where it provides essential lubrication and is burned in the combustion process. As much as 30 percent of this gas/air charge is released through the open exhaust port as hydrocarbon emissions.

The two stroke direct fuel injected engine has been modified to prevent these harmful emissions from being released into the environment. According to George L'Heureux, Infmeum's small engines technical service advisor, "In two stroke direct fuel injected engines, unlike the traditional two stroke, the fuel is injected directly into the combustion chamber and burned while the exhaust port is blocked by the piston at the top of its stroke. This prevents unburned fuel from escaping through the exhaust port, resulting in significant emissions reduction.

"Because the fuel no longer passes through the engine to help carry the oil and provide additional cooling, direct fuel injected engines are more highly stressed and operate at higher temperatures. While OEMs have gone to great lengths to ensure that their fuel injected engines can operate on TC-W3 oil, they recommend their genuine oils for optimum performance."

Genuine oils are those oils that are selected by the OEMs and marketed under their own name. The oils meet TC-W3 specifications and provide an additional source of revenue for OEMs, but they are not necessarily the best quality oils available for the application.

The two stroke oil requirements for direct injection engines remain unchanged from the requirements of traditional two stroke engines. In fact, Jay Patel of Lubrizol notes, "OEMs see no need for new TC-W3 specifications and the existing ones are likely to remain in place for the foreseeable future. Testing is so costly that formulations aren't likely to change either, except in relatively minor ways. NMMA read-across guidelines are quite flexible compared to automotive guidelines. As long as the viscosity characteristics remain similar, planned formulation changes can be done under read-across rules."

The new four-stroke outboard engines work much like automotive engines in that they are lubricated by a circulating multi-viscosity oil and require oil changes after a certain period of time. Four stroke outboards easily meet the EPA's 2006 emissions standards, and they are also quieter and up to 40 percent more fuel efficient than two stroke motors. However, they are also 30 percent more expensive, heavier and more complex, making maintenance more difficult.

According to Yamaha's Steve Friedrich, "If you pull your boat out of the water in the winter, it's a snap to change the oil. But if you don't pull it, it's pretty difficult to change the oil and in some engines, impossible. The larger engines are designed so that it allows the oil to be changed with ease while the boat is in the water. Also, many outboard engines are used in remote locations and disposing of used oil there may be difficult and wind up dumped."

FC-W (Four Cycle-Water) is the unofficial term for the new marine engine oils currently being developed specifically for four stroke outboard engines. Like TC-W3 oils, they will be licensed by NMMA.

According to NMMA's Schultz, some issues need to be addressed before official licensing begins. "First, is the problem of viscosity dilution," he says. "Four stroke outboard engines often have long periods of idle, and in cooler water the oil tends to accumulate enough fuel which then dilutes the viscosity and may lead to excess wear unless the additive package is fortified with extra surface active ingredients, like ZDDP, which contains phosphorous and zinc. In cars, the operating temperature is high enough, around 220 degrees Fahrenheit, to 'cook off the fuel but in marine engines the operating temperature is between 120 and 145 and at that temperature the fuel does not get vaporized as easily.

"Automotive additive packages in API SJ oils, which is the category currently recommended for most of today's marine four stroke engines, can handle the oil dilution issue. But with substantial reductions in the percentage of ZDDP in future automotive engine oil categories under active consideration by the auto industry, marine applications may be placed at risk," says Schultz.

"And we can't simply increase the thermostat temperature because that will cause the second problem," continues Schultz. "At about 160 degrees F. salt water starts to recrystalize inside the cooling system and begins to form stalactites and stalagmites and impede the flow of coolant. Some ingenious technological solutions have been devised, such as rerouting the oil through engine hot spots to give it the ability to shed fuel. But cooling system problems can be a major issue."

Friedrich chairs the NMMA subcommittee in charge of creating FC-W specifications. He says, "We're trying to come up with an oil specification specifically for marine applications, which have special requirements and face a far harsher environment than faced by land applications. We're looking for a product that will specifically address oil dilution and provide more rust control inside the engine."

A variety of bench and engine tests will be used in setting the FC-W oil specification, but none of the TC-W3 tests will be included. "We will look at passenger car motor oil [tests], that is ASTM-supported tests possibly including Sequence IV A for wear control," explains Friedrich. "And we will introduce a 'no harm' test in which an engine will be run for a specified time and load and then stripped and examined to see if any harm has been done. Our members are now in the process of determining which manufacturer's engine is best suited for this purpose and setting criteria and specifications."

Initial specifications for FC-W are expected to be completed by February, but no time has been set for the introduction of FC-W oils on store shelves.

AMSOIL Synthetic 2-Cycle Oils and Formula 4-Stroke Synthetic Motor Oil are formulated to withstand the harsh operating conditions faced by modern outboard motors. Formulated with superior synthetic base stocks and advanced additive packages, AMSOIL Synthetic 2-Cycle and 4-Cycle Oils provide the ultimate in protection and performance, keeping friction, heat and wear to an absolute minimum, while preventing problems such as oil dilution and rust.