Riviera Boat Magazine

New Mercury 4.6L V8 Outboard

In advance of Mercury’s announcement last Friday of its new V8 4.6L 4-stroke engine, BoatTEST spent two days inspecting the new engines. We tested seven different boats, each with a different engine configuration.

The result is that we have a pretty good idea of what these new engines offer and the best applications for them. Over the next several months we will be running complete reports on the engines and boats we tested. Today we start with an in-depth look at what sets the new Mercury V8 apart from other outboards on the market..

Key Features

  • Highest displacement in its class
  • Lightweight
  • Digital Throttle and Shift (DTS)
  • Sleek, angular design
  • Engineered for quiet operation
  • Transient Spark Calibration for More Torque
  • Adaptive Speed Control
  • Advanced Range Optimization
  • Sporty Exhaust Sound Control


Mercury 4.6L V8 Outboard Platform (Outboard) Specifications
Type of Engine 4-Stroke
Number of Cylinders 8 Cylinders
Shaft Length Options 20” (50.8 cm) / 25” (63.5 cm) / 30” (76.2 cm)
CARB Rating 3-Star
Recommended Fuel 87 Octane
Alternator Output 115 Amps total


Mercury has introduced an all-new 4.6-liter (279 cubic inch) V8 engine. The company says the naturally aspirated outboards will provide smooth, quiet power and optimize fuel economy, all in a package with a dry weight package ranging from 505 lbs. to 600 lbs. (229 kg to 272 kg), in the lightest weight units available of each of the four series. The powerhead is a large-displacement designed for more power and greater low- and mid-range torque, and for better acceleration. It’s 35 lbs. (16 kg) lighter than the previous-generation Mercury Verado 300, an inline-6 configuration.

This new platform, along with the new V6 launched in February, replaces the 2-stroke OptiMax and the L6 supercharged Verado, except for the L6 350 Verado and 400R Racing engines.

Mercury Verado 4.6L V8 quiet


The Mercury Verado 4.6-liter V8 300 has multiple seals for quieter operation.

Key Features

  • Highest displacement in its class
  • Lightweight
  • Digital Throttle and Shift (DTS)
  • Sleek, angular design
  • Engineered for quiet operation
  • Transient Spark Calibration for More Torque
  • Adaptive Speed Control
  • Advanced Range Optimization
  • Sporty Exhaust Sound Control

Mercury 4.6-Liter V-8 Verado 300-hp Outboard Specifications

Horsepower: 300

Type of Engine: 4-stroke

Number of Cylinders: 8 cylinders

Configuration: V-8, 32 valve DOHC

Weight (lb./kg): 505 – 600 lb. / 229.06 – 227.16 kg

Displacement (liter/cubic inch): 4.6 liter / 279 cubic in.

Gear Ratio: 1.85:1 or 1.75:1

Shaft Length Options: 20” (50.8 cm) / 25” (63.5 cm) / 30” (76.2 cm)

CARB Rating: 3-Star

Recommended Fuel: 87 Octane

Alternator Output: 115 Amps total

Mercury Verado 4.6L V8


The Mercury Verado 300 can be used in single- and multiple-engine installations.

Mercury Outboards: The Big Picture

Mercury has introduced its next generation of large outboards and the company has based the new models on two displacement sizes and configurations, a 3.4-liter V6 and a 4.6-liter V8. These 4-stroke engines will be sold under the Mercury brand lines FourStroke, Verado, Pro XS, and SeaPro, as well as the Mercury Racing brand. Their horsepower ranges from 175 to 300, depending on the platform.

The concept driving these outboards is to offer a compelling amount of power by means of displacement, fuel injection, and electronic engine control. The electronic system is used to dial-in fuel efficiency. It does this by controlling the fuel-air mixture in a closed-loop fuel system. For more torque at the low end and better hole shot times, Mercury is using what is known as a “Transient Spark”, which the company says will give the engine 5% to 7% more torque at the low end.

Mercury Verado 4.6L V8 horsepower


The V8 Verado outboards are available in 250- and 300-hp models, and use Mercury’s Advanced MidSection to reduce vibration and noise.

Four V8 4-Stroke Outboard Lines

FourStroke. Mercury’s 250- and 300-hp FourStroke outboards are built on the 4.6-liter V8 platform, while the 175-, 200-, and 225-hp FourStroke outboards are built on the 3.4-liter V6 platform. These engines are designed for use on pontoon boats, sportboats, center consoles, dual consoles and other applications where lighter weight (24 lbs. lighter than the V6 Yamaha), better torque, and reliability are important.

Mercury Verado 4.6L V8 horsepower


The V8 platform is available in 11 different models ranging from 200- to 300-hp.Pro XS.

The Pro XS engines are designed primarily for bass, multi-species, and bay boats. Here, many consumers want fast hole shot times as well as high top speeds, something that is difficult to produce with the same prop. Mercury’s solution is lightweight – 505 lbs. (229 kg), the brand’s lightest V8 engine. The torpedo has been redesigned for reduced drag, and a Torque Master unit is optional. And a transient spark calibration is said to increase torque somewhat. This line of outboards gets a 175 based on the 3.4-liter V-6, and the 4.6-liter V8 platform is used in four models — rated for 200, 225, 250, and – for the first time – a 300-hp model. This line of engines replaces the 2-stroke OptiMax engines, which will no longer be made.

mercury_verado46lv8platform_displacement_2018.jpg This Mercury Pro XS 250-hp outboard is built on the 4.6-liter V8 platform and has the greatest displacement of any outboard in its class.SeaPro. Designed specifically for commercial applications, which means that it is more ruggedly constructed in the hub, and has options that are not available in some of the other models. The SeaPro line gets a 200-hp outboard based on the 3.4-liter V6, and three choices built on the 4.6-liter V8 platform: a 225, a 250, and a 300-hp model. Both the Advance MidSection and the Conventional MidSection (CMS) are available on SeaPro units.

Mercury Verado 4.6L V8 advanced


The Mercury Verado 4.6-liter V8 300 outboard, with its distinctive silver Advanced MidSection is compatible with Mercury’s Joystick Piloting system.Verado.

The Verado takes its name from the famous L6 supercharged engine it replaces, but it is not supercharged and because of its large displacement, lightweight and transient spark ignition, it doesn’t need to be. Nevertheless, it is Mercury’s premium engine of the four lines, and it has its own set of standard and optional features designed for its intended market. Most notable is the fact that it comes standard with the Advanced MidSection, a 5.4” gearcase, electro-hydraulic power steering and additional sound abatement in its cowl. It is also the only recreational engine that can use the Joystick Piloting system.

It has been specifically designed for saltwater in single and multi-engine applications for center consoles, express fish boats, and express cruisers where consumers want lots of quiet power. The engines can be installed on 26” centers – 2.5” less than on V6 Yamaha engines – making this engine more advantageous for quad installations.

Design Innovation

The Powerhead. Much of the innovative design of the 4.6-liter V8 platform comes from the mandate for the new line: It had to be powerful, have high torque at the low end, be lightweight, quiet, and efficient. Consider that the 4.6-liter V8 is 2 liters greater than the supercharged 2.6-liter displacement of the inline-6 Mercury and yet it weighs 35 lbs. less. Displacement is the way to generate more torque in a 4-stroke engine, a job that the supercharger fulfilled in the L6 2.6 models. The double-overhead cam design, with four valves per cylinder, combines with an enlarged intake to deliver plenty of air and fuel when it’s needed.

Mercury Verado 4.6L V8 cam design


The double-overhead-cam design has four valves per cylinder, and its natural balance may help play a role in quiet operation and reduced vibration.

The Fuel Injection System

These new outboards use two intake valves to charge each cylinder, with the injector for each cylinder positioned between them in the intake manifold. We asked Mercury why the injectors were placed in the manifolds instead of in the cylinders themselves. The answer–

“A port fuel injection (PFI) system has many advantages, chief among those being simplicity, reliability, and cost,” says Brian Meyer, category manager for 75+ hp outboards for Mercury Marine. “Direct injection (DI) systems certainly can improve fuel economy and performance of an engine. However, Mercury has chosen to address the performance needs of our customers by optimizing the displacement and efficiency of our PFI engine, while also employing our Advanced Range Optimization (ARO) technology. We believe that the ARO system yields comparable improvements in fuel economy to a DI fuel system at a significantly lower cost.”

Mercury Verado 4.6L V8 fuel injection


This detail shows Mercury’s port fuel injection, which places the injector, indicated by the green arrow, between the valve stems on the intake ports. Mercury says that this design has proven to be reliable and cost-effective.

Unusual Exhaust System

This is one of the most innovative aspects of the engine because it reduces the width of the engine, reduces its weight, and helps contain engine noise – all with one design. The exhaust manifold is in the middle of the V, instead of being on the outside. It is then routed from the top of the engine, down the centerline, between each side of the V of the engine. This allowed Mercury to keep the cowl width slimmer so that the outboard could be installed on 26” centers – 2.5” less than its primary competitor.

Mercury Verado 4.6L V8 exhaust


The exhaust emerges from the engine abaft the alternator, using the centerline instead of an outboard route.The exhaust-system design uses two separate, multi-chamber mufflers located beneath the “chaps,” as the manufacturer calls the panels on either side of the midsection. The port side has the muffler for the exhaust for normal operation. On the starboard side is the idle-relief muffler, using a port aft to reduce backpressure at low rpm.

Mercury Verado 4.6L V8 chambers


Multi-chamber mufflers are concealed under midsection panels at locations indicated by yellow arrows. The idle-relief exhaust port is indicated by the green arrows.

Sport Exhaust

Boating is meant to be fun, and sometimes boaters want to hear the throaty growl of a V8 (or two), letting everyone know they’re there. Mercury designed Verado to be exceptionally quiet, and never is that more apparent than when using a setting called Sport Exhaust. When it’s turned on, on the VesselView touchscreen, the system routes exhaust through the idle relief and one of the two mufflers.

Let’s Rumble. This creates an unmistakable throaty rumble that’s been tweaked to impress friends and neighbors and call attention to the new outboards – to say nothing of the boat’s proud owner. And when it is toggled off, the outboards sounded even quieter than we initially thought. It’s a system that Mercury says has never been offered on an outboard before.

Mercury Verado 4.6L V8 sport exhaust


Turn on the Sport Exhaust with a touch of the screen on the Mercury VesselView display.

Top Cowl Service Door

Perhaps one of the more noteworthy features of this new outboard line is the watertight hatch in the top of the cowl to provide access to the dipstick as well as the oil fill. There’s a decal outlining service requirements along with a QR code to allow a smartphone to link to additional service information.Mercury Verado 4.6L V8 hatch

A watertight hatch in the cowl opens with a simple press to reveal the oil dipstick and fill.

Easy-Off Cowl

Under the top cowl service door, there’s a handle that lifts with a red button. Lifting that handle releases the latches all around the cowl, so it can be lifted off easily.

Mercury Verado 4.6L V8 cowl


Beneath the top cowl door is a red button that releases the handle to remove the cowl.Mercury Verado 4.6L V8 handle


The handle pops up, providing something to grip while also releasing the latches all around the base of the cowl.

Mercury Verado 4.6L V8 cowl


Using the handle, simply lift the cowl free.Mercury Verado 4.6L V8 cables


From the underside of the cowl, the handle, indicated with the green arrow, is connected via cables to the latches, shown with yellow arrows that secure the cowl to the engine.Mercury Verado 4.6L V8 latches


This image shows the cowl latches, as well as the cabling that controls them, and the seals that keep the noise in and the moisture out.

Ease of Maintenance

Once the cowl is removed, many service points are apparent. The oil filter is easy to spot near the fuse box on the port side. The spark plugs are arrayed in neat columns aft and the fuel filter is handy there as well, on the starboard side.

Mercury Verado 4.6L V8 maintenance


This maintenance decal beneath the cowl shows the 100- and 300-hour service requirements in an intuitive, graphical representation.Mercury Verado 4.6L V8 spark plugs


The port-side spark plugs are indicated by the four green arrows, while the yellow arrows show the long runners of the air intakes, which pack air into the engine for better combustion, according to Mercury.

Mercury Verado 4.6L V8 fuse box


The fuse box and oil filter are prominently displayed on the port side of the outboard.Mercury Verado 4.6L V8 rigging door


Another feature that will endear this outboard to riggers, the addition of a rigging door, shown here with a green arrow, to simplify the process of running the throttle-control and fuel lines into the engine.

More Net AMPS than Any Engine in Class

All four lines of V8 have 115 AMP alternators. But the name of the game is “net AMPs” – the AMPs left over from the running of the engine to power onboard accessories, electronics, and to keep the batteries fully charged. At WOT these alternators produce 90 net AMPs, we’re told. At high cruising speeds they produce 65 net AMPs. These are high numbers and are important for owners of well-equipped boats, particularly the larger cursing boats that are now being fitted with outboard engines. But, that’s not all…

Idle Charge Battery Management

The alternator on the Verado 4.6-L engine has a maximum output of 115 AMPs. At idle the alternator provides 20 AMPs for the boat.

Simply put, the engine-management system detects when the batteries drop below acceptable levels due to increased power draw. Today’s boats have more electrical and electronic devices on board than ever before, and they all require a flow of clean juice to keep operating properly. Whether the onboard systems are charging trolling-motor batteries, keeping the sound system thumping, or running big-screen helm electronics including a chart plotter, CHIRP sounder, and radar, the system increases idle rpm to boost alternator output, to help charge batteries to compensate for power draw. It gently raises the idle level from 600 rpm to around 800, to get to the next level on the curve of the alternator, and in this mode, it delivers 30 AMPs of usable power to the house batteries. While the engine is revving slightly higher, it’s still at a speed where it’s able to shift.

Mercury Verado 4.6L V8 alternator


The alternator on the 4.6-liter V8 platform, indicated by the green arrow, provides the boat with up to 30 AMPs of usable power at high idle.

Lower Unit

The lower unit gearcase on the FourStroke and Pro XS outboards is the 4.8” unit. 5.4” gearcases are standard on Verado and SeaPro, but is available as an option on the other two lines. The robust 5.4” gearcase is an evolution of the one that has been used on previous Verado models and has proven itself in tens of thousands of hours of rugged use over the last few years.

Mercury Verado 4.6L V8 lower unit


The lower unit accommodates a robust 5.4” gearcase on the Mercury Verado 300 and has proven to be quite reliable.

Adaptive Speed Control

This proprietary system maintains engine speed regardless of condition, and Mercury has the system patented. The idea is that the rpm remains constant even when seas are rough, the driver puts the boat into a hard turn, or a tow sport requires steady power. Adaptive Speed Control is a function of the ECU, where operator demand and engine load are measured and the electronic throttle position is adjusted. It is standard on all of the engines.

Mercury Verado 4.6L V8 running


The Mercury Verado 300 keeps its rpm level steady on hard turns when Adaptive Speed Control is used, and our test captain was delighted that incremental throttle adjustments were no longer needed.

Advanced Range Optimization – Improves Fuel Efficiency

Because the outboard uses a digital throttle control, it can also improve its own fuel economy. It begins when the system detects a steady-state mode, where the driver isn’t adjusting the throttle constantly. Once the operator variable appears to be set, the digital control tunes the throttle plate and the spark to lean out the fuel burn to maximize fuel economy, optimizing the boat’s range. It is available on all of the engines.

mercury_verado46lv8platform_running2_2018.jpg With Advanced Range Optimization, the operator can leave the throttle alone and let the engines step up the efficiency. Mercury Verado 4.6L V8 ob install


Mercury says it has a wide variety of available props to help tune any outboard installation for performance and efficiency for virtually any application.

Digital Control

All four of the V8 lines are rigged with SmartCraft Digital Throttle and Shift (DTS), which gives the responsive control by wire. In multiple-outboard installations, Joystick Piloting for Outboards can be made part of the Verado package, offering simple fingertip control around the dock.

Mercury Verado 4.6L V8 dts


Verado outboards use Mercury Digital Throttle and Shift control, as well as Joystick Piloting for Outboards.

Mercury Verado 4.6L V8 joystick piloting


Our test captain used the Joystick Piloting system on the Mako 284 CC rigged with twin 300-hp Verado outboards around the dock. Controls by Wire.

A Note About Active Trim

While expert drivers may sneer at the idea of the optional Active Trim, it has been shown to work in our testing, and can even offer something to those who may think their feel for boat trim is more effective than that of a computer: Active trim synchs up the trim of the engines, letting the expert trimmer tune the rig more effectively, rather than dealing with trim motors that adjust the engines at varying rates in a multiple-outboard installation.

Mercury Verado 4.6L V8 active trim

Active Trim lets the user choose from five preset trim profiles to accommodate a variety of sea and load conditions. The green arrows show the Active Trim control window on a VesselView display. This image is from our test of a twin-engine installation.


The outboards have received a three-star emission rating from CARB, and are compliant to the U.S. and E.U. regulations as well, all on one calibration.

Mercury Marine’s Corrosion-Resistant Aluminum Alloy

Historically, outboard engines in salt water have suffered from corrosion. When electrons flow through dissimilar metals the weaker metal is eaten away or corrodes. Outboard engine blocks, cylinder heads, gear cases, driveshaft housings and swivel brackets are made out of an aluminum alloy by all manufacturers. But all aluminum alloys are not the same.

Mercury Verado 4.6L V8 corrosion

Corrosion protection on the Verado 300 (shown in Cold Fusion White) keeps the outboard looking good and running the way it should.Low-Copper Alloy is Key. Mercury’s die-cast components, are all made from XK360 aluminum-silicon alloy. The same goes for the new 4.6L block of this outboard platform, which is made with a high-pressure die-casting in a 4,500-ton press, which is among the largest in the world. This process shows significant investment by Mercury and contributes to the weight loss of the new engines. Mercury is generally regarded to have the best corrosion-resistant alloy in the recreational marine industry. All four lines use the same alloy.

Quiet Operation

The new V8 platform has been designed to be light, but also to keep its noise to itself. The design starts blocking noise with the cowling – and the Verado has more sound abatement qualities than the other models, we’re told. The entire outboard is sealed to keep engine noise in. The engines all use an air intake that’s baffled to be quieter. Mercury has been using a variant of this design since it introduced the Verado line, and it works.

All of the lightweight parts used were designed to also keep sound in, including the plastic valve covers to mask the noise of the valves and injectors.

Mercury Verado 4.6L V8


Mercury says all parts in its new outboards were designed with an eye toward reducing sound levels and weight.Another way to keep the outboard quiet is to engineer less internal friction into its design. Mercury says its engineers designed the oil-flow scheme and sized the bearings with this in mind.

Damping Vibration

Mercury looked closely at the mounting system on the mid-section of the outboard and calculated where the vibration comes from on the engine. Engineers determined the vectors of vibrational force, i.e., whether the vibration is moving fore and aft, or athwartships, or some angle in between. The engineers then designed the mounts to offset that vibration at a suitable angle. Because of this analysis, the mounts can be engineered to be firmer, rather than just softer to damp any vibration – and in this way they are also designed to maximize engine performance, says Mercury.

Mercury Verado 4.6L V8 verado


Verado outboards use the Advanced MidSection design (identifiable by its silver color), which cradles the engine and minimizes the vibration that is transferred to the boat.

Advanced MidSection

The new Verado has what Mercury calls an Advanced MidSection (AMS). It is a next-generation enhancement and a step up from the Conventional MidSection (CMS) used on the FourStroke outboards, and it is a next-generation version of the mounting system initially developed for the L6 Verado. The AMS uses perimeter mounts to damp vibration and contain noise, and it has a multi-piece welded structure that reduces its size and weight. This allows the Verado to have electro-hydraulic steering, and makes them compatible with the company’s Joystick Piloting system in multiple-outboard setups. The Verado outboards are standard with Mercury’s Digital Throttle and Shift controls.

Mercury Verado 4.6L V8 mid section


The Advanced MidSection was designed as a response to the vibrational forces created by the engine, and reduces the amount of energy transferred to the boat’s transom.

Choice of Colors

It may not seem like a huge development, considering what some other outboard manufacturers have done with custom finishes and even LED lights. But it wasn’t so long ago that Mercury owners were told they would void their warranty if they painted their outboard anything but Phantom Black.

Mercury has introduced three shades of white – Cold Fusion White, Warm Fusion White, and Pearl Fusion White — in addition to its traditional black engine color.

Mercury Verado 4.6L V8 phantom black


Phantom Black is still offered, but three different white engine colors are offered. Four accent panels can liven up the package, as shown here from left, Graphite Grey, Mercury Silver, Pacific Blue, and Redline Red.There’s also an accent panel that comes in four colors – Pacific Blue, Graphite Grey, Redline Red, and Mercury Silver – plus a ready-to-paint accent-panel option that boatbuilders and dealers will use to custom-match a hull color.

Mercury Verado 4.6L V8


The Mercury FourStroke and Verado outboards are available in four base colors, and this FourStroke outboard is Warm Fusion White with an accent panel custom-painted to match the hull.

VesselView Simrad Electronics Integration

The propulsion system diagnostics are integrated into the Mercury VesselView display, which is a Simrad unit rebadged for Mercury. Some boats will be able to integrate the engines into the Simrad helm electronics and not require a standalone display. The Simrad units have a specific, branded Mercury engine page. Screen sizes run from 7” to 24” (.18 m to .61 m).

The touchscreen unit lets the user tap with a fingertip to open a display window on the left side of the helm screen with a number of data categories which can be set to display consistently across all functions, including chartplotter, fishfinder, and radar displays. Speed data is available and any tap will bring out more detailed information. The display screen also offers analog-looking gauge treatments.

Mercury Verado 4.6L V8 vesselview


The Mercury VesselView touchscreen gave access to a wide range of features offered by the integrated outboard system.

Advanced Features Electronic Control

The Simrad-Mercury VesselView interface allows the operator to set Mercury’s proprietary electronic control features, including Cruise Control, which allows the user to set a speed or rpm and have the engine maintain it, and Troll Control, which will let the engines slow-troll down to 550 rpm. Additionally, the Active Trim system can be set to tune engine trim to optimize efficiency.

Mercury’s Skyhook Advanced is also available, with different settings that allow different levels of control in specific situations and are easily downloaded via Wi-Fi connection – and advantage over the competitive brands that require dealer installation.

  • Heading Adjust lets joystick users adjust the heading in 1- and 10-degree increments while using Skyhook, for precise control.
  • BowHook maintains a boat’s position, while unlocking the boat from a set heading. This allows the boat to find the best position to minimize engine use while station keeping, in relation to wind and current.
  • DriftHook will maintain the boat’s heading, but let the boat drift, allowing the same 1- and 10-degree increments while drifting, if Heading Adjust is also on the system.


Remote Oil Checks

Mercury’s VesselView engine monitor helm display lets the user know the oil level is fine prior to the first startup of the day. The system only works if the engines are in the down position and the oil temperature indicates the engine is cold, since a tipped up engine or one that is warm wouldn’t get an accurate reading, so it won’t work each time a boat starts throughout the day.

Mercury Verado 4.6L V8


The VesselView display shows the oil level is fine prior to startup. Note this display shows a twin-engine installation.

Moving Prop Alert

As an option, Mercury has added a Moving Prop Alert system, which consists of a unit outfitted with LED lights mounted on the aft engine housing. The LEDs illuminate when the engine is running, and an LED prop graphic animates and appears to turn. As quiet as these outboard engines are, this makes sense, especially when one considers the joystick and position-holding systems that move and operate engines beyond the driver’s direct control. The engines are prewired for this addition, and multi-engine boats that use skyhook have it added at the boatbuilder or dealer level.

Obviously, the engines should not be turned on when swimmers are in the water and close to the boat. It is, nevertheless, an important safety feature in our opinion.

Mercury Verado 4.6L V8


Mercury outboards come prewired for the optional Moving Prop Alert, which tells swimmers near the stern of a boat when the engines are running and when the props are turning.

This article was written by boattest.com

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