Beginning with the launch of the GB30 in 1964, Honda introduced a series of outboard motors powered by environmentally friendly four-stroke engines. At the time, however, the marine market was dominated by two-stroke outboard motors, and Honda’s four-stroke models faced disadvantages in both weight and cost.

Even so, Honda steadily expanded its lineup of environmentally responsible four-stroke outboard motors. In 1971, Honda introduced the 45TWIN and 75TWIN, followed in 1977 by the BF100, a 10-horsepower model powered by a 197cc four-stroke engine. This established a compact outboard lineup ranging from 2 to 10 horsepower.

Meanwhile, the market had already begun shifting toward higher-output two-stroke outboards, with 55hp, 85hp and even 200/225hp models appearing. For Honda, the lack of products in these high-demand horsepower ranges became a major challenge.

To respond to market demand, Honda launched an internal initiative known as the “MS Project” and began development of new mid-range outboard motors producing 35 and 45 horsepower.

In 1990, Honda began sales of the 808cc BF35A and BF45A in Europe, North America and New Zealand. These models became the world’s first four-stroke outboard motors in the mid-range horsepower category. Combining advanced environmental performance with low noise levels, they earned the IMTEC (International Marine Trades Exhibit and Conference) Innovation Award at the Chicago Boat Show and attracted global attention.

In 1993, strict emissions regulations known as the “Lake Constance Ship Regulations” were introduced on Lake Constance, which borders Switzerland, Austria and Germany, as part of efforts to improve water quality. While the lake was a major tourist destination, it also served as a source of drinking water for communities along the Rhine River. Since the 1960s, pollution from domestic and industrial wastewater had become a growing problem, leading not only to stricter wastewater treatment standards but also emissions regulations targeting marine leisure craft operating on the lake.

At the time, the global marine market was overwhelmingly dominated by two-stroke outboard motors. Compared to four-stroke engines, two-strokes emitted lower levels of NOx (nitric oxide and nitrogen dioxide), but significantly higher levels of hydrocarbons (HC), which were considered a major contributor to water pollution. As a result, complying with the new Lake Constance regulations using two-stroke technology proved extremely difficult, prompting manufacturers to pursue four-stroke solutions.

The Lake Constance regulations were introduced in stages, with the first phase taking effect in 1993 and the second phase in 1995. Honda’s four-stroke outboards, however, had already complied with the second-stage requirements by 1992. The first model to achieve this was the BF8B, an 8-horsepower model sold in four Nordic countries. In 1993, the mid-range BF40B also cleared the regulations. This demonstrated the environmental advantages of the four-stroke technology Honda had adopted since its very first outboard motor.

Following Europe, the United States — the world’s largest marine market — introduced the EPA Federal Air Regulations for Marine Vessels in 1998. Honda’s entire U.S. outboard lineup complied with the regulations. Moreover, Honda achieved the final emissions targets required by 2006 in the very first year of implementation, 1998.

Compliance with both the Lake Constance regulations and EPA standards brought increased attention to Honda outboards, and global production volumes rose steadily from 1993 onward. Cumulative production, which stood at approximately 250,000 units in 1993, surpassed 400,000 units in 1994 and reached 700,000 units by 1999. As environmental awareness expanded worldwide — not only regarding marine pollution but also air quality — Honda became increasingly recognized as a manufacturer of “clean, high-quality outboard motors” and as a leading company in four-stroke outboard technology.

Around this time, demand for high-output four-stroke outboards also began increasing in the marine market. In response, Honda expanded its mid-range lineup in 1995 with the introduction of the BF75 and BF90, powered by a 1,590cc engine producing 75 and 90 horsepower respectively.

To address growing demand for higher-output four-stroke outboards, Honda also established a unique strategy: developing large-displacement outboard engines based on Honda automobile engines. This approach leveraged the strong reputation Honda automobiles had built in Europe and North America. Technologies already proven for performance and reliability in Honda automobile engines were adapted for marine use, and Honda actively pursued the marinization of automobile technologies.

As a result, in 1998 Honda introduced the BF115 and BF130, powered by a marinized version of the 2,254cc engine used in the Honda Accord. In 2001, Honda launched the BF225 flagship model, producing 225 horsepower from a 3,471cc engine. The BF225 significantly exceeded the stringent 2008 emissions regulations established by the California Air Resources Board (CARB), which were considered even stricter than EPA standards.

The BF225 was based on the 3.5-liter V6 engine used in vehicles such as the Lagreat. Equipped with technologies including PGM-FI electronic fuel injection and VTEC variable valve timing, it created a positive cycle in which Honda’s latest automobile technologies were increasingly adopted for outboard motors as well.

With this, Honda’s four-stroke outboard lineup expanded to 15 models ranging from 2 to 225 horsepower, capable of meeting a wide variety of needs — from commercial applications such as sightseeing and fishing boats to leisure uses including cruising and sport fishing.