New Mercury muscle

Chris Beattie | VOLUME 26, ISSUE 6

Mercury chose the Club Marine Mandurah Boat Show to debut its new 150hp FourStroke.

In the lead-up to this year’s Club Marine Mandurah Boat Show, boating journalists received an intriguing invitation from the folks at Mercury hinting at something big in the offing. Apparently there was to be a release of some significance at the show and we were requested to set aside some time for a “very special event”, as one Mercury rep mentioned.

As it turned out, it was a measure both of the growing significance of the Club Marine Mandurah Boat Show and the Australian boating market, that Mercury chose the event to host the southern hemisphere’s launch of its new 150hp FourStroke EFI outboard engine.

Mercury is extremely proud of its latest big powerplant, emphasised by the scale of the launch in Mandurah, where it had two boats equipped with the new 150 FourStroke and a host of staff on hand. Both boats were Kiwi-built craft, one a fiberglass Fi-Glass 6.4 Warrior cuddy cab and the other an aluminium 6.1m craft from Surtees.

Prior to our on-water demonstrations, we were given a thorough technical presentation on the new engine.

An in-line, four-cylinder engine measuring 3lt in capacity, it is the largest displacement 150hp currently on the market, according to Mercury, which also claims that it offers unprecedented durability under all conditions and delivers superb fuel efficiency and tremendous performance. It employs a relatively conventional top end layout, with a single overhead camshaft controlling two valves per cylinder operated by finger-style rockers. The simple design helps reduce overall weight in comparison to more commonly employed multi-valve, twin overhead cam layouts.

“We listened to what boaters were asking for and then set out to build the ultimate 150 horsepower FourStroke outboard,” said Mark Schwabero, president of Mercury Marine. “The finished product is an engine that is incredibly durable – more durable, in fact, than any other 150 four-stroke ever built – but is more compact than the engines of our competition. It delivers great fuel efficiency and tremendous performance.”

Weighing in at just 206kg, Mercury says its new outboard is by far the most compact four-stroke 150hp outboard in the world. In comparison, the new engine is just 11kg heavier than Mercury’s OptiMax 150hp direct-injected two-stroke.


Mercury says the new 150 FourStroke’s many attributes make it the perfect option for owners wanting to repower their boats, especially older models with transoms not designed to accommodate the weight of some of the heavier four-strokes now on the market.

According to Mercury, the new 150 is designed, built and tested to be one of most reliable and durable engines in the world. It has been put through its testing paces in such severe conditions as cold 20-foot swells off Canada, commercial fishing in the warm waters of the Bahamas and the unprotected seas around Guadeloupe, in the French West Indies.

“It’s easily handled thousands of hours of hard-core severe duty, real-world testing in applications the average boat operator will never endure,” says Mercury.

A primary aim for the design and engineering team was to produce a compact engine that would also produce a strong torque curve.

“The new Mercury 150 is class-leading in every respect, but we particularly focused our attention on being a stand-out in the areas that our customers told us really matter – quality and reliability, smooth operation, a great torque curve, low weight and compact size, plus excellent fuel economy,” said David Foulkes, vice president of engineering at Mercury.

The 150 FourStroke is fitted with a new alternator charging system that is fully regulated and supplies current only on demand; when the system senses battery voltage has dropped below 14.2 volts, the alternator will engage and re-charge the battery. The automotive-style alternator develops more than 67 per cent of its 60 amp output at only 1000rpm. When the alternator is not charging, it ‘free-spins’, which minimises the power drain on the engine and unnecessary heat build-up.

Starting is via Mercury’s SmartStart system, in which the operator simply turns the key and immediately releases it. SmartStart automatically continues turning the engine until it starts.

There is also an internal balancing system featuring balance shafts coupled directly to the crankshaft. Drive is via “bulletproof high grade steel” gears, according to Mercury.

Another new feature is an idle exhaust relief system, which helps reduce noise by employing a “low pass acoustic filter” that attenuates high frequency exhaust noise at idle speeds.


A new 4.9in gearcase has been designed, which Mercury claims is built to withstand the demands of up to 300hp powerplants. The larger and more robust internals required a bigger gearcase, but Mercury says it has been designed with an ultra-efficient hydrodynamic profile for decreased drag. In fact, says Mercury, the 150 FourStroke’s gearcase housing, while significantly larger in diameter and longer in torpedo length, features better hydrodynamics than gearcases found on 90-115hp-class outboards.

A new Focus mount system, in which the mounts are located farther from the powerhead, significantly reduces mount temperature and increases mount durability, according to Mercury. The upper pair of mounts are also angled, which is claimed to significantly reduce vibration transmitted to the hull. In addition, this allows easier inspection and servicing, without the need to remove the powerhead.

The new 150 also boasts a compact and lightweight thermo-bonded SMC composite top cowl to protect the powerhead from the elements. The powerhead also features builtin alignment points to help cowl removal and installation while avoiding snagging electrical components such as harness wires.

The 150’s transom brackets are of the very highest quality, says Mercury, and are 22 per cent heavier than those found on equivalent 150hp outboards.

For our water test, the seas off Mandurah were relatively benign, although a freshening westerly drove some large swells onshore. The lack of chop at least allowed us to wind out the 150 FourStroke on both platforms and I was immediately impressed by its power and torque delivery down low – not surprising given it’s 3lt capacity. For those requiring good holeshot, this motor won’t disappoint, and it lifted both craft onto plane with no effort, whatsoever. Throttle response throughout the mid-range wasn’t lacking either. Torque is what this engine is all about and its large capacity delivers it with a minimum of fuss over a wide rev band.


Using the Fi-Glass for our performance figures, it would seem that the 150 FourStroke will also find favour with those with a sharp eye on fuel consumption. In the mid range, from 3000 to 4000rpm, it delivered figures of 13.3lt/hr (3000rpm), 17lt/hr (3500rpm) and 25lt/hr at 4000rpm – not bad for an engine of this capacity and good figures for anyone who tends to cover a lot of water. Performance was good, with the combination delivering 49km/h at 4000rpm, 63km/h at 5000rpm and a maximum of 76km/h at 5900rpm (WOT). And given the combination of its large displacement and four-cylinder configuration, it was relatively quiet overall.

Mercury claims the 150 FourStroke is the world’s easiest 150hp outboard to rig, with standard mechanical cables, dual cable or hydraulic steering compatibility, optional power steering on dual-engine setups, and the ability to run on either standard analog or full SmartCraft instrumentation straight from the factory. All connections under the cowl for throttle and shift cables, data harnesses etc, are easily located and accessed for quick, intuitive, hassle-free rigging. It’s also compatible with Mercury’s Big Tiller system.

Repowering is also quick and easy, says Mercury, with the 150 able to be connected to any steering, Mercury rigging or instrumentation currently in the boat, or whatever the customer wants to upgrade in the dash or console.

Mercury underpins the durability of the new 150 FourStroke with a 3+2=5 year fully-transferable, non-declining engine warranty, plus its 3 year corrosion warranty.

First shipments in Australia and New Zealand are expected in January, 2012.