New Mercury V10 5.7L 350 and 400 Horsepower Verado Outboards

Industry leading Mercury Marine is known for forward thinking, having come up with barrier-breaking outboard engines like the V12 600 horsepower Verado, which remains the most powerful outboard engine in production today. And recently they charged right over yet another hurdle, developing the world’s first V10 outboard. These naturally-aspirated 350- and 400-hp Verados were developed to replace Mercury’s current V6 engines occupying this powerband, which rely on superchargers to develop added oomph.

mercury verado v10 outboard
Behold, the all-new Mercury Verado V10. Photo via Plantation Boat Mart.

Mercury V10 Verado Specifications

This all-new 5.7-liter platform displaces 349 cid and is designed to run 87 octane fuel through its closed-loop system, to a full-throttle maximum of between 5800 and 6400 rpm. Available shaft lengths include 20”, 25”, 30”, and 35”, and the prop swings through a 2.08:1 gear reduction. Weight is 695 pounds, which is a major victory considering that this is a mere 27 pounds over the V6 Verados producing the same horsepower.

freeman 42 with mercury verado v10 400 hp outboards
A full range of shaft lengths means the new V10 Verado can be matched up with everything from huge powercats to small bowriders. Photo via Lenny Rudow.

How do you add all those cylinders without a whole lot more weight gain? Mercury engineers say a number of the parts were lightened up but a key factor is the extensive use of computational fluid dynamics, which allows for the removal of materials without affecting strength or reliability.

Mercury uses the same 64-degree cylinder angle in the V10 as they do in their 6.4-liter 250- and 300-hp V8, which keeps the motor svelte enough to mount on standard 26-inch spacings. The engine also shares some of the V8’s major design structures including quad-cam and four-valve cylinder heads. Also like the V8, electro-hydraulic power steering compatible with Joystick Piloting, complete SmartCraft technology, plus perks like Adaptive Speed Control (which maintains engine rpm as load varies due to interaction with the seas), and auto-trim are integrated. Some other major system components, however, such as the lower unit, are very different in nature from the V8.

New Tech in the Mercury V10

Speaking of the lower unit: the V10 gets a completely new one, designed to maximize lift and quickly bring large, heavy boats up on plane. It also gets a new Revolution X 18” to 33” pitch propeller to match, along with a deeper 2.08:1 gear ratio versus the V8’s 1.75:1 ratio. Gear case diameter is 6.4” and it’s longer than previous units, boosting lift.

mercury v10 verado outboards
The V10 Verado in 300 hp and 400 hp models sports an all-new lower unit and propeller. Photo via Lenny Rudow.

The new gearcase is interesting, but perhaps the biggest new feature of this motor is its ability to more or less replace a generator. The stock alternator is a beefy 150-amp unit, which provides gobs of juice — that’s about double the charging power of the engines it’s replacing. Swap that out for an optional dual-mode 12/48-volt upgrade, however, and the V10s can power a Fathom lithium-ion e-power system. This incorporates batteries, switching, distribution, and control and monitoring, and can provide all the juice you need to power things like appliances, climate control, gyroscopic stabilization, and entertainment systems. While this involves a substantial design and equipment investment by the boatbuilder, it can completely eliminate the need for generators and their fuel systems.

Another major tech investment in the Mercury V10 350- and 400-hp outboards is mitigation efforts for what the company calls “NVH,” for noise, vibration, and harshness. In trying to make the boating experience more pleasurable, Mercury prioritized finding ways to make the V10s as smooth and quiet as possible. This begins by isolating the powerhead from the boat via their “Advanced Midsection,” which supports the powerhead with perimeter mounts and reduces the transmission of vibrations into the transom. A tuned air intake reduces induction noise, and injection sound is muffled. Mercury claims these efforts result in a motor that’s 45-percent quieter at cruise versus a leading competitor. While we didn’t measure the V10s sound levels directly against competitors when we ran them (and thus can not verify the exact percentage), we did feel that a major reduction in sound levels at cruising speeds was obvious and evident.

Testing the Mercury 350 Verado and 400 Verado

Upon its introduction we ran both model outboards on a variety of boats of different types and sizes. In all cases, including a 42-foot quad-engine offshore fishing power catamaran, there was zero hesitation coming up onto plane. The torque curve feels more or less flat through the powerband, delivering the same punch whether you’re initially hitting the throttles or advancing through the midrange.

mercury verado v10 350 on a sea ray slx 260
While running the V10 350 hp Verado outboard on a Sea Ray SLX 260, we found the engine quiet and smooth. Photo via Lenny Rudow.

When it comes to NVH, it absolutely seems that Mercury has hit the mark. While most four-strokes are quiet at idle this isn’t always the case at higher RPM ranges, but the V10s seem to make little more noise than the boat’s hull moving through the water. The electro-hydraulic steering is virtually effortless, and they system on the whole does in fact improve the boating experience.

How these motors hold up over the long haul remains to be seen, but considering that the V8 (launched in 2018) has a strong track record thus far, it seems fair to have high expectations.

See Mercury Verado V10 outboards for sale on Boat Trader.