Power Players

When it comes to marine propulsion, a lot has changed in 60 years. Six decades ago, the sterndrive was still a new idea, a 100-hp Kiekhaefer Mercury was the most powerful outboard money could buy, and a diesel inboard often belched soot that coated a transom with an oily film. By comparison, today’s engines are cleaner, quieter, more efficient and would be unimaginably powerful to a boater in the early 1960s.

Two factors have influenced the evolution of marine propulsion: intense competition between key players in the market and the government imposition of exhaust emissions regulations. In fact, the technology created to control auto emissions has enabled the development of today’s clean, easy-starting and very powerful gasoline and diesel marine engines. And in the future, the investments auto manufacturers make in hybrid and electric vehicles will likely trickle down to marine power, fueling the next evolution in propulsion. As we anticipate that leap forward, let’s take a look back at 60 years of marine engines and celebrate the developments that have shaped today’s powerboating experience.

1964 Kiekhaefer MerCruiser II

The modern sterndrive was introduced as the Volvo Penta Aquamatic 100 at the 1959 New York Boat Show. It paired an inboard 100-hp Volvo engine with a transom-mounted outdrive that was steerable and tilted “to combine inboard efficiency and safety with outboard flexibility and speed.” The Aquamatic also offered 30 more horses than Mercury offered in an outboard. Kiekhaefer Mercury countered in 1961 with the MerCruiser sterndrive, packaged with marinized Chevrolet auto engines at 120 and 140 hp. In 1964 a more robust MerCruiser II drive was offered directly to boat builders with familiar American engines rated up to 310 hp—three times the power of any contemporary outboard.

1982 Volvo Penta Duoprop

Borrowing an idea from the torpedo, the Volvo Penta Duoprop sterndrive featured contra-rotating propellers on a common shaft, first for diesel engines and later with gasoline. Twin props offered more blade area and thrust than a single prop, with better control at low speeds, especially in reverse, ideal performance for larger cruising boats. In 1995 MerCruiser introduced its twin-prop Bravo Three drive. Duoprop and Bravo Three remain on the market, and Suzuki and Mercury feature contra-rotating props on their most powerful outboard models.

1990 Mercury HP525SC

Following the acquisition of Kiekhaefer Aeromarine by Brunswick Corporation, Fred Kiekhaefer led an effort to transition Mercury Hi-Performance from racing into the production of engines for high-performance pleasure boats, a segment booming in the wake of the Miami Vice television show frenzy. One of the first was the MerCruiser Hi-Performance HP525SC, the first mass-produced supercharged and warrantied marine engine. The 7.4-liter V8 was rated at 490 hp on 92 octane pump gasoline. By 1992, Hi-Performance would add 600- and 750-hp supercharged engines to the line that would power a generation of performance craft.

1991 Honda BF45

Through the 1980s, all popular outboards used a two-stroke powerhead burning gas-and-oil fuel, a combination that produced tremendous hydrocarbon emissions. In the early 1990s outboard manufacturers were given about 10 years notice that emissions regulations would be forthcoming. This raised debate inside engine companies. The premise of the outboard motor was that it was lightweight for its power; manufacturers could not imagine how a four-stroke engine would ever be light enough. At Mercury and OMC, there were factories with teams of engineers tooled up to manufacture two-stroke engines. But when Honda introduced its 45-hp four-stroke in 1991 it got attention from other manufacturers. The three-cylinder, 808cc BF45 weighed about 200 pounds and was much smoother, quieter and more fuel efficient than contemporary two-strokes. Honda followed with a BF90 model in 1998, pitching its four-stroke motors as “Power in Tune with Nature.” They were a hit with freshwater anglers who, with a Honda on the transom, could troll for hours without inhaling two-stroke exhaust smoke.

1995 Common Rail Diesel Fuel Injection

A desire to reduce exhaust emissions in auto and truck diesel engines revived interest in an old idea—the common rail injection system. The advent of modern electronic engine controls made it possible to replace traditional mechanical diesel injectors with a hollow rail of highly pressurized fuel running the length of the cylinder head. The rail fed each individual fuel injector, which opened and closed under control by the engine computer. Fuel delivery was thus optimized for engine speed and load, unlike mechanical injectors, which were designed to perform best at full throttle. The high-pressure common rail system atomized fuel into very fine particles that ignited easily and burned completely, significantly reducing emissions. Nippondenso introduced the first common rail system for truck engines in 1995, and the technology was soon appearing on marine diesels from Volvo Penta, Caterpillar, Cummins and others. The system was further refined with the introduction of pulse injectors, which delivered fuel in multiple bursts in each cycle.

1996 Two-Stroke Direct Fuel Injection

Doubting the viability of a large four-stroke outboard and stuck in the prevailing two-stroke culture, Mercury Marine and OMC chose to pursue a low-emissions two-stroke solution: direct fuel injection (DFI). The system would inject atomized fuel directly into the combustion chamber, timed electronically to prevent unburned fuel from escaping through the exhaust port, the main source of hydrocarbon emissions. The Mercury OptiMax 200 with DFI debuted in early 1996, and Evinrude and Johnson models with Ficht RAM DFI came to market in 1997. Yamaha would introduce its HPDI (High Pressure Direct Injection) DFI two-stroke models in 2000. Each company’s DFI technology cut emissions by about 30 percent, enough to meet the EPA 2006 emissions regulations, and improved fuel efficiency by 30 percent. Both the Ficht and OptiMax motors experienced early technical issues. Those afflicting OMC were more dramatic and contributed to the 2000 bankruptcy of the company. BRP acquired the Johnson and Evinrude brands and technology and brilliantly re-engineered the DFI system as Evinrude E-TEC. Citing near-complete customer preference for four-strokes, Yamaha dropped its HPDI two-strokes in 2015. Mercury replaced its last OptiMax Pro XS models with new V6 and V8 four-strokes in 2018. BRP persisted on the two-stroke track, introducing Evinrude G2 motors in 2014, but after 20 years of trying to win over boaters with DFI technology, BRP discontinued Evinrude production in 2020.

1998 Joystick Control

The joystick has been called one of the 20th century’s most distinctive contributions to the interface between people and machines. A cultural breakthrough initially related to flight, a lot of manufacturers saw it could be used for other things, including Hinckley Yachts. In 1998, the builder introduced its Jetstick, a joystick that simultaneously integrated control of the boat’s main jetdrive and side thrusters. With it the driver could rotate the boat almost within its own length or slide it directly sideways to snug up to a dock. Later, in 2005, the era of digital joystick controls arrived with the introduction of the Volvo Penta IPS. In 2007 the Cummins MerCruiser Zeus pod drive was introduced with all-digital controls that included the Smartcraft Joystick Docking System. Both IPS and Zeus achieved the level of close-quarters maneuverability offered by the Hinckley Jetstick, but without the use of thrusters.

Digital steering and throttle/shift control made the joystick possible. With constant refinement by Volvo Penta, Mercury Marine and Dometic Seastar Solutions, joystick control is now available for all steerable propulsion systems. Linking digital steering with GPS has enabled station-holding features and digital autopilot systems. Today, we are on the cusp of workable autonomous docking and avoidance systems that are made possible by being able to independently control the steering, shifting and throttle of multiple engines.

1999 Yamaha F115

Yamaha pushed the four-stroke outboard further into the mainstream with its F115 model. It applied casting technology developed for its new 450cc four-stroke motocross motorcycles to reduce powerhead weight. At 401 pounds the F115 was 40 to 50 pounds heavier than a DFI two-stroke, but about 70 pounds lighter than a four-stroke Honda BF115. The Yamaha was very smooth and quiet. As four-stroke outboards became more powerful and were rigged to larger boats, the weight difference became less significant. In 2001 Yamaha introduced a V6 F225 four-stroke that was as compact and lightweight as a two-stroke.

2004 Mercury Verado

Mercury placed its four-stroke bet on the all-new supercharged 2.6-liter Verado, and it turned out to be a winner. Originally designed to produce 275 hp, the Verado would go through five generations of development, get boosted to 400 hp, and remain in the Mercury line for 19 years, an astounding lifespan for any engine. In two decades it earned a bulletproof reputation. The Verado also debuted with two key features: electro-hydraulic power steering and digital controls. Its narrow profile allowed multi-engine mounting on 26-inch centers, its in-line-six engine was silky smooth and the supercharger produced impressive low-end thrust.

2005 Volvo Penta IPS

Volvo Penta changed the inboard game in 2005 with the introduction of its Inboard Performance System (IPS), a steerable “pod drive” designed to replace direct-drive and V-drive inboard power in boats with twin engines ranging in length from about 37 to 50 feet. IPS was initially offered as a complete system with the Volvo Penta D6 diesel engine, a propulsion unit with gearbox and forward-facing contra-rotating props, drive-by-wire steering, throttle/shift controls and an information screen for the helm. Compared to traditional inboards, IPS offered reduced drag for improved efficiency and improved control at all speeds. The propulsion units were electronically steered individually to help track the boat through turns, and the dual props offered outstanding thrust control at low speeds.

2007 Yamaha F350

At its introduction the 5.3-liter V8 Yamaha F350 was the most powerful and, at 804 pounds, heaviest outboard ever produced. Rather than design this engine for speed, Yamaha tuned it like a locomotive, with gobs of low-end power to swing a big propeller and lift a heavy boat on plane—it produced 45 percent more thrust than an F250. To prove its concept, Yamaha rigged a pair of F350 motors on the transom of a Grady-White Express 360 in place of the usual triple F250 motors. Here was a motor that could replace inboard power on heavy offshore boats with a significant weight reduction, ease of maintenance and repower, and the ability to trim and tilt above the water. The inboard engine bay could be redesigned as a mid-cabin or a huge fish box. Boat builders started imagining the possibilities.

2007 Indmar ETX/CAT

Adapting automotive exhaust catalyst technology to inboard marine engines proved to be challenging. A catalyst functions at a very high temperature, not an issue when it’s exposed to the air below a car or truck, but a potential problem in the confines of a boat engine bay. The very hot catalyst might also be destroyed if it came in contact with water used to cool the exhaust system. In addition, this type of emissions control system relies on an oxygen sensor in the exhaust system that would also have to be moisture-resistant. Indmar Products, an engine supplier to the inboard tow boat segment, developed a patented exhaust manifold that prevented water inversion and was dry up to the catalyst. This manifold made it possible for Indmar to meet the 2008 California Air Resources Board (CARB) Four Star-Super Ultra Low exhaust emissions rating. Today all gas inboard and sterndrive engines are catalyzed.

2010 Mercury Racing QC4

Mercury Racing took sterndrive performance to a new level with the introduction of the Quad Cam Four Valve (QC4) 1350, a proprietary 9.0-liter twin-turbocharged V8 mated to a new robust M8 drive and electro-hydraulic transmission. Rather than build up an automotive engine, Mercury Racing designed a custom aluminum engine block with bore and stroke selected to produce massive torque and high-revving horsepower, double overhead cam heads with four valves per cylinder, and premium internal components. The result: reliable race-bred power backed by a warranty and Mercury Marine service. Today the QC4 is offered from 860 hp to a dual-calibration 1,350/1,550-hp model.

2011 Seven Marine 557

Taking the big outboard idea to the extreme, former Mercury engineering lead Rick Davis teamed with son Eric and manufacturing specialist Sandy Ballou to introduce at the 2011 Miami International Boat Show the Seven Marine 557, a 557-hp outboard with a supercharged GM 6.2-liter V8 engine under its cowl, a ZF transmission and a gearcase from Selva. Presented on the transom of an Intrepid 370 Cuddy typically powered by triple 300-hp motors, the Davis team suggested a pair of the Seven Marine 557 outboards could replace four 300- or 350-hp motors, offer about 300 less horsepower but also weigh 668 pounds less, and significantly reduce drag by placing only two gearcases in the water. Of course, the boat owner could also rig three or four Seven Marine motors on the transom of even bigger boats, which is exactly what happened. A Seven 627 would follow, and in 2017 Seven Marine was acquired by Volvo Penta, only to be shut down in 2020, just months before the introduction of the Mercury V12 Verado 600. In the past decade, the advent of ever more powerful outboards has changed the pleasure boat market in North America, almost completely supplanting the sterndrive and enabling previously unimaginable performance from large day boats and cruisers.

2014 Volvo Penta Forward Drive

Always the innovator, Volvo Penta created its Forward Drive specifically to enable wake surfing behind a sterndrive-powered boat, an alternative to a very expensive inboard tow boat. The Forward Drive features contra-rotating props facing forward so they are located below the boat hull where they are unlikely to threaten a fallen wake surfer. MerCruiser immediately countered with its similar Bravo Four S drive.

2021 Mercury V12 Verado 600

Mercury flexed its engineering muscle to create this clean-sheet execution of the Seven Marine concept, a motor with massive displacement designed to produce impressive thrust and lift heavy boats on plane. A 7.6-liter V12 powerhead produced 600 horsepower, transmitted through a two-speed automatic transmission with a low range for outstanding hole shot and high range, paired with up to 37-pitch contra-rotating props, for speed and economy. Instead of steering the entire motor only the gearcase steers to enable 27-inch center-to-center spacing plus 45 degrees of steering range port and starboard to maximize low-speed control authority in joystick mode.

2022 Rotax S Series

Not long after shutting down Evinrude, BRP revealed its new Rotax S outboard, a 115/150-horsepower motor with a horizontal powerhead designed to fit below a swim platform. The two-stroke powerhead had E-TEC DFI and was enclosed in a watertight casing. The Rotax S addressed the last objection many customers had to outboard power—that it cluttered the swim platform. Now available for BRP’s Manitou Max pontoon models, expect to see more powerful versions of the concept in the future. 

NANNI INDUSTRIES & REPOWERING

Not every boater appreciates a digitally controlled engine. Enter Nanai Industries, a Franco/Italian diesel engine marinizer founded in Milan in 1952. Now distributed in the U.S. by Kraft Power of Pompton Plains, New Jersey, Nanni offers a range of emissions-compliant engines from 10 to 1,150 hp based on Kubota, Toyota, Scanla and John Deere engines. The smaller Kubota-based engines all feature mechanical injection. "These Tier 3 diesels are very popular for repower with cruising sailors and powerboaters who want to be able to repair the engine themselves. You don't need a factory tech and a scan tool to work on them," says Brook Streit of Kraft Power. "A lighting strike is also not going to knock out one of these engines." Streit says the larger Nanni conversions are popular for repower because they are compact and lightweight, "We've repowered a number of Bertram 31s with the 270-hp Nanni T4270, which is based on a a 9-liter, four-cylinder Toyota engine with common rail injection. Nanni engines are also original equipment in models produced by Fortier, Hinckley, Beneteau, Swan Lagoon, Ball, Fontaine Pajot, Hanse and others." -CR

This article was originally published in the February 2024 issue.