Four-stroke outboards to the fore

With marine-engine environmental regulations looming on the horizon, Mercury Marine broke the low-emissions outboard barrier in 1994 with 9.9hp and 50hp four-stroke models.

The newcomer engines premiered at the New York Boat Show, exactly 54 years after the very first Mercury outboards were introduced to the boating world. Targeted at anglers with an emphasis on fuel efficiency, smooth idling, quiet operation and impressive durability, the four- strokes were touted for their smoke-free operation and the ability to run on “straight gas,” far easier than two-strokes’ 50:1 gas/oil fuel mix.

At cruising speed, the 50hp FourStroke decreased fuel consumption by 30 percent compared to two- stroke outboards and could troll at just 750 rpm as a result of its four-cylinder design. The early Mercury FourStroke engines were originally manufactured jointly with Yamaha; Mercury provided the block, crankcase, crankshaft and connecting rods, while Yamaha produced the cylinder heads for the 50hp. The 9.9 was built with a Yamaha powerhead. Both models were completed with Mercury mid-sections and gearcases.

Entering the market early allowed Mercury to educate its customers about the coming technology changes. Boat companies, dealers and consumers had to adjust to the idea of heavier four-stroke outboards; a concern that is virtually nonexistent today.

Mercury Marine continued to develop its own four- stroke technology, applying it across its larger horsepower engines. When the phased-in environmental regulations on marine engines took effect in 1996, Mercury was able to meet the new requirements with a complete four-stroke outboard line, complemented by its first-to-market, low-emissions, direct-injection two-stroke OptiMax technology. Today, Mercury’s FourStrokes are second to none; in fact, they’re absolute game changers.

The Mercury 150 FourStroke is widely acclaimed for its durability and light weight, piling up thousands of hours of severe, real-world field testing in extreme conditions during its development stage. Mercury Verado, the world’s only inline six-cylinder, 24-valve double overhead cam, supercharged FourStroke production outboard, was created entirely from scratch to be the most technologically advanced outboard motor on the water.

In 2018, Mercury introduced high-horsepower four-stroke outboards in Verado, Pro XS, FourStroke and SeaPro brands to remarkable accolades from the industry and consumers.