Mercury - 4.6L V-8 Outboards – FourStroke . Verado . ProXS . SeaPro

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Captain's Report

Mercury 4.6L V-8 Outboards

Mercury Marine announced a new 4.6L V-8 outboard platform to complement the 3.4L V-6 platform that was introduced in February.

The new V-8 4.6L naturally-aspirated 4-stroke engine platform was the result of listening to what consumers, boat dealers and builders wanted, according to John Pfeifer, Mercury Marine president, who said today, “This new lineup aligns with what consumers are asking for and we are delighted to deliver it to them.” He also said, “These engines…provide options for the consumer that they’ve never had before.”


Mercury 4.6L V-8 Outboards
Pictured here is the new 300-hp V-8 Verado on a Yellowfin 24 bay boat.

1. New 250 & 300-hp FourStroke


The new 250- and 300-hp V-8 FourStroke outboard engines are “high-tech without being high-stress,” says Mercury. The high-displacement, quad-cam design of the new V-8 powerhead generates greater torque, especially in the mid-range, a Mercury spokesperson said. “The 300-hp FourStroke delivers up to 9% more torque than the nearest competitor at 3500-4500 rpm.”


Large Displacement but Lightweight


This V-8 platform not only has the highest displacement in its horsepower class – 10% more than the Yamaha 4.2 L – but, the 300-hp model is 10 lbs. (4.5 kgs.) lighter than its closest competition.


The new FourStrokes are also versatile, offering consumers choices between mechanical or digital (DTS) controls and hydraulic or power steering. This versatility makes them appropriate options for repowering a wide range of different hulls.


Mercury 4.6L V-8 Outboards
The new Mercury FourStroke and Verado lines come in three shades of white (plus Phantom Black), with four accent-panel colors available, as well as an accent panel ready for custom painting.

Color Options


The new V-8 FourStroke engines are also available in multiple colors and can be further customized with the addition of an accent panel. Mercury’s new colors are: Warm Fusion White, Cold Fusion White, and Pearl Fusion White options plus the ever-popular, traditional Phantom Black. Five factory accent color panels are available, plus there are “paint-ready” panels, which let owners paint their own panels to personalize their engine. These choices are available for both the V-8 FourStroke and the V-8 Verado outboard engines.


Appropriate Applications. The FourStroke engines are primarily targeted to sportboats, pontoon boats, center and dual consoles, and multi-species fishing boats.


Mercury 4.6L V-8 Outboards
The heart of the new 4.6 L V-8 features 32 valves and double overhead cams. Fuel is injected into the intake ports.

Additional Features



  • Digital or mechanical controls.

  • 87-octane unleaded fuel standard.

  • Advanced Range Optimization improves cruise-speed fuel efficiency by automatically adjusting fuel delivery.

  • Idle Charge Battery Management: When battery voltage is low, the engine will automatically increase idle rpms to boost alternator output and recharge batteries to the proper level, protecting operators from draining their battery while trolling.

  • Electronic Oil-Level Sensor: When the ignition key is turned, an optional electronic oil-level sensor automatically alerts operator to low oil level.

  • Top Cowl Service Door simplifies routine maintenance with easy oil checks and oil fills without removing the cowl. The Top Cowl Service Door also houses the latch release and a carrying handle.

  • Easy Maintenance: A graphic, hour-based maintenance decal, no-spill oil drain & filter, color-coded maintenance points, and Mercury’s maintenance-free valve-train reduces operating expense.

  • Adaptive Speed Control: Automatically maintains a desired rpm or speed regardless of changes in load resulting in increased throttle response.


Mercury 4.6L V-8 Outboards
The Pro XS comes in four horsepower sizes, and in any color desired, so long as it’s Phantom Black.

2. New 175-300-hp Pro XS


Mercury's Pro XS offering is directed to competitive anglers, and the V-8 platform joins the 3.4 L V-6 175-hp Pro XS that was introduced in February. The new 4-stroke 4.6 L V-8s come in 200-, 225-, 250-, and 300-hp versions, completely replace the 2-stroke OptiMax engines, which are no longer in production.


"The unveiling of these powerful, high-horsepower Pro XS models culminates a process we began in 2016 to comprehensively elevate the entire Pro XS brand with engineering that delivers higher performance, better fuel economy, uncompromising reliability and durability in a light-weight four-stroke design," said John Buelow, Mercury Marine vice president of global category. "We now have a complete family of top-performing Pro XS outboards from 115- to 300-hp that competitive anglers will love," he said.


Obviously, the replacement for the OptiMax had to have high low-end torque, high top speed, and light weight (505 lb./229 kg.).


Mercury 4.6L V-8 Outboards
The new Mercury Pro XS was designed to give competitive bass tournament anglers everything they want in an outboard engine without much compromise.

Targeting the Bass Boat Market


Tournament bass-boat customers are a demanding breed and they want high low-end torque for fast starts as well as high wide-open-throttle speeds, two objectives that are hard to achieve with the same prop.


Mercury’s solution was to create the largest-displacement engine in class then tune it from 200 to 300-hp, rate the engine up to 6200 rpm, keep the engine light at 505 lb. (229 kg.), and design a new gearcase with a robust 1.25-inch prop shaft with low-water pickups in the nose cone, and reduce the number of pickups on the side of the hub for less drag. The unit is designed to be run at high speed with a minimum amount of hull in the water. The unit is also available with a next-generation Torque Master gearcase that offers a 1.75:1 gear ratio.


The Pro XS has virtually all of the features of the FourStroke, the ones mentioned above, plus it comes in Phantom Black at no extra charge.


Mercury 4.6L V-8 Outboards
The new Mercury Verado series is targeting the offshore fishing-boat market and is particularly well adapted to multi-engine installations.

3. New 250- & 300-hp Verado


The new 250 and 300-hp V-8 Verados are Mercury’s premium offering and these engines come equipped with numerous state-of-the-art features. They have almost no resemblance to the old Verados, which were made famous by their low displacement and superchargers.


The V-8 Verados are compatible with Mercury Joystick Piloting for Outboards for easy maneuverability and control. The Verado series is the only one of the four that offers a joystick option. All of the features available on the FourStroke series mentioned above, also come on the Verado.


The Verado comes standard with electro-hydraulic power steering for smooth operation and simplified rigging. The robust 5.4” gearcase comes standard, as well.


Advanced Mid-Section


The new V-8 models’ next-generation Advanced Mid-Section (AMS) incorporates perimeter mounts that deliver what Mercury says is the “lowest vibration in the industry…and 60% less than the leading competitor’s 300-hp engine.” While we are not able to measure vibration, we believe this is probably true given the remarkable engineering and structure of the mid-section which is, indeed, advanced from anything we have seen on other outboard engines. This is proven technology as it was used on the old supercharged Verados.


Mercury 4.6L V-8 Outboards
The red arrow points to the air intake and the plenum directs the air down through noise-reducing baffles to the intake manifold runners. The blue arrow points to the exhaust, which goes down the back of the engine to the hub. The yellow arrow points to the 115-amp alternator, which puts out a net 90 amps at WOT.

Exclusive “Sport” Exhaust


While Mercury engineers have certainly worked hard to reduce engine noise, they also realize there are times when some owners like to announce their arrival or departure with a throaty rumble that could only come from eight large-displacement cylinders. A touch of the control screen closes off one of two mufflers and diverts the exhaust through the idle-relief port. This is the first time that an outboard engine has had such a device, we’re told.


Appropriate Applications


Being the top-of-the-line engine series with virtually all of the available features either as standard or optional equipment, the Verado is the most versatile of all four of the V-8 lines. It can be used for offshore fishing boats and high-speed sportboats, as well as bay boats and tri-toon pontoon boats.


Offshore Ready. It is an obvious choice for owners of large offshore center consoles for both single and multiple-engine applications. Because of its slim body, it can be mounted on 26” centers – 2.5” less than on the Yamaha V-6 300, which mounts on 28.5” centers. This is an important consideration in triple and quad applications.


Mercury 4.6L V-8 Outboards
The new 300-hp Verados were made for the challenges of offshore running where speed, reliability, and fuel efficiency are all important.

With more and more large cruising boats being designed for outboard power, a brace of Verado 300s is a viable option for these applications. Given its torque advantage over other 4-stoke engines (because of its greater displacement, if nothing else), it should be a good performer when matched with these types of boat.


All Alloy is Not the Same. While rarely discussed, the proprietary aluminum alloy formulation, which is low in nickel, that Mercury uses in all of its engines, has maximum corrosion-resistance and is generally regarded in the industry as the best alloy in saltwater.


Mercury 4.6L V-8 Outboards
The SeaPro is ruggedly constructed to stand up to the arduous demands of commercial applications all over the world.

4. SeaPro


Mercury’s new 225-, 250-, and 300-hp SeaPro engines are designed for commercial applications of all types. Mercury has calibrated the new V-8 SeaPro models to produce plenty of torque at lower rpm levels, enabling users to work their outboards hard without placing excess stress on the engine, according to a company spokesperson. We’re told that true to SeaPro’s workhorse heritage, the new 225- to 300-hp V-8 SeaPro models are engineered to deliver years of trouble-free performance.


For Heavy Duty. Mercury says that these engines are manufactured with heavy-duty components to cope with the demands of global commercial operation – including a gearcase that is validated at three times the lifespan of a recreational gearcase.


Advanced Mid-Section (AMS). The new SeaPro is available with Mercury’s exclusive Advanced Mid-Section (AMS), which moves engine mounts aft and outward to virtually eliminate vibration from being transmitted to the boat. Models equipped with the AMS also feature electro-hydraulic power steering and are compatible with Mercury’s Joystick Piloting system. The Conventional Mid-Section comes standard.


Other Features


The SeaPro series of engines may also be equipped as standard or optional with most of the equipment and functionality mentioned above. Additionally, Mercury says that SeaPros have an industry-leading warranty for commercial users that includes protection against corrosion, a significant advantage over competing products.


More to Come


BoatTEST.com has recently tested most of the new Mercury 4.6 L V-8 engines in a number of applications. These tests and an in-depth look at both the V-8 and V-6 platforms will appear in the future. Stay tuned.


If you have a question about Mercury’s new V-8 4.6 L engine, just ask …