Mercury 150hp FourStroke: Review

With the recent debut of the Mercury 135hp FourStroke outboard, it seems timely to revisit its larger 150hp sibling. Launched more than three years ago now, the big-displacement in-line four-cylinder Mercury four-stroke has proven a huge success – and is now powering all manner of craft around the world – from high performance bass boats to party pontoon craft.

OVERVIEW
- Taking the market by storm
When it was released in late 2011, the Mercury 150hp FourStroke was heralded as a break-through design. The lightweight, compact Mercury promised a new level of performance, closer aligned to traditional two-stroke outboards – such as the DFI Optimax in Mercury’s own two-stroke line-up.

Has it delivered? By all accounts, and from our personal experience, the answer to this question is a resounding yes.

DESIGN SPECS
- Big displacement, light-weight, compact profile, fewer parts
In designing the Mercury 150hp, Brunswick eschewed the small displacement, supercharged engine configuration of its Verado four-strokes in favour of a normally-aspirated, EFI engine with a class leading 2998cc displacement. In terms of cubic capacity, the next nearest competitor is the Suzuki 150hp – which displaces 2867cc.

The large displacement configuration of the Mercury gives it significant low-down torque for excellent hole-shots and impressive mid-range pick-up.

In design specifics, the Mercury 150hp is an in-line four-cylinder engine with a single overhead camshaft arrangement with eight valves.

The Mercury has a bore and stroke of 102mm x 92mm and a low gear ratio of 1.92:1.

Multi-port EFI provides a very efficient fuel delivery, ensuring it has excellent economy throughout the rev range.

Competitor brands use a double overhead cam, 16-valve engine format, but Mercury opted against this engine design and went for the single overhead cam layout (in combination with eight over-sized valves).  This is simpler in design with excellent low-down torque from high displacement in this case and fewer moving parts to help reduce servicing and hopefully owner maintenance costs.

The simpler design also saves weight, a very important consideration in the market place, given the customer misconception that four-strokes are still over-weight compared with their two-stroke counterparts.

At 206kg for the lightest version, the Mercury 150hp is the lightest four-stroke in its class for now – and only 11kg heavier than Mercury’s DFI two-stroke Optimax 150hp.

Next best four-stroke is the Suzuki DF150 which comes in at 215kg in standard longshaft configuration.

The compact, lightweight design of the Mercury makes it ideal as a repower engine. It will fit in tight outboard wells on weight sensitive hulls and it can be rigged with mechanical or hydraulic steering, and with traditional analogue instruments as well as the very latest Mercury Smartcraft digital gauges.

The Mercury 150hp has been built with durability firmly in mind. For example, the transom mounting brackets are heavier and the engine mounts larger than competitor brands. The mounts are also designed for reduced vibration at low and high rpm.

More evidence the Mercury is over-built is in the heavy-duty gearcase – which uses components originally designed for the 300hp Verado, an engine producing twice the power output.

Corrosion protection is taken care of with Mercury’s patented XK360 low copper content alloys combined with an eighteen step paint application process that is claimed to be the best in the business.

PRICE AND EQUIPMENT
- A well priced, full featured four-stroke with low maintenance costs
Leading Gold Coast Mercury outboard dealer, Nitro Marine has the Mercury 150hp available with prices starting from $20,400 for a standard 508mm (20”) longshaft. This price includes control box, analogue gauges and full fit-up.

Add just $100 for the extra-longshaft 635mm (25”) version.

This fully-fitted pricing undercuts most competitor four-strokes on the market so it is little wonder the big displacement Mercury is so popular with new boat buyers and the repower market.

Servicing costs are also down compared with other four-strokes in this power segment, and this is largely due to the simpler engine configuration – which does not require valve clearance adjustments for example.

You can also save money by doing some of the routine servicing work yourself – including changing the oil and filters. The layout under the cowl is user-friendly and everything is clearly marked. There is even a chart/decal attached to the powerhead with the maintenance schedule itemised.

With regard to features the Mercury 150hp has everything we have come to expect from a modern outboard including alarms and warnings for every possible failure or engine ailment, along with features like a cowl mounted trim switch, instant, one-touch starting (hot or cold), easy release engine cowl, start-in-gear protection, analog or digital instrumentation, and a counter-rotating option for a twin engine installation.

To run your onboard electronics and keep the battery fully charged, the belt-driven alternator provides a class leading 60 amps of power.

For big open deck boats, the Mercury 150hp is available as a tiller-steer outboard with Mercury’s Big Tiller system which has optional power steering and a range of great user-friendly features.

POWER & PERFORMANCE
- Strong performance and economy across a range of platforms
We have now tested the Mercury 150hp FourStroke in a variety of conditions across a range of different platforms. We have tested it on an 8.0m pontoon craft, several mid sized fibreglass bowriders, and even with a twin engine installation on our recent test of a Mako 234 Centre Console.

Throughout, the Mercury 150hp has excelled, with a power delivery that is as close to an old-style two-stroke as we have yet found – with regard to hole-shot acceleration and mid range throttle response.

Importantly, this level of performance now comes with greatly improved efficiency and economy, along with easy starting, low emissions and no smoke.

For this engine review we have drawn upon our experiences with the Mercury 150hp on a variety of different boats. The latest was a CSB Huntsman 6000 Series.

On this excellent kiwi-made craft, the Mercury 150hp performed as well as ever – smooth, quiet, powerful and frugal on fuel.

We ran a series of performance tests using a GPS and Mercury’s Smartcraft engine instrumentation to record a best engine fuel economy figure of 1.33 nautical miles per litre while running at 3000 rpm and a speed of 19.0 knots.

On the test boat, this equated to a maximum range of 126.2 nautical miles on 95 per cent of the boats 100-litre fuel tank.

We also recorded a top speed of 40.8 knots at 5600rpm – at which point the engine was consuming just 53.5 l/ph.

For reference, in the above tests the Mercury was fitted with a 17” pitch S/S Enertia propeller.

VERDICT
- A very special four-stroke outboard for new boats and repowers
It has been over three years since the introduction of the Mercury 150hp FourStroke, yet, remarkably, it remains the benchmark in its class. Its combination of power and performance, with economy, simplicity, light weight and ease of maintenance, remains unchallenged by Mercury’s four-stroke competitors.

The Mercury 150hp is the four-stroke of choice in the repower market for boats in the 5.5 – 6.0m size range, and it delivers equally well when coupled with new boats in a range of sizes and applications. It’s a versatile outboard, and one that has now earned its stripes and accolades.

PERFORMANCE - SPEED
4.2kts (7.8km/h) @ 1000rpm
5.9kts (10.9km/h)@ 1500rpm
7.1kts (13.1km/h) @ 2000rpm
11.7kts (21.6km/h) @ 2500rpm
19.0kts (35.1km/h) @ 3000rpm
23.7kts (43.8km/h) @ 3500rpm
27.6kts (51.0km/h) @ 4000rpm
32.0kts (59.2km/h) @ 4500rpm
35.3kts (65.3km/h) @ 5000rpm
40.0kts (75.0km/h) @ 5500rpm
40.8kts (75.5km/h) @ 5600rpm (WOT)

PERFORMANCE – ECONOMY
3.6 l/ph @ 1000rpm
5.4 l/ph @ 1500rpm
8.6 l/ph @ 2000rpm
11.7 l/ph @ 2500rpm
14.3 l/ph @ 3000rpm
18.1 l/ph @ 3500rpm
24.1 l/ph @ 4000rpm
31.4 l/ph @ 4500rpm
38.6 l/ph @ 5000rpm
52.0 l/ph @ 5500rpm
53.5 l/ph @ 5600rpm (WOT)

MAXIMUM RANGE ON 95 PER CENT OF 100-LITRE FUEL TANK: 126.2nm @ 3000rpm

Specifications:
Pricing: $20,400 including longshaft 508mm (20”) configuration with control box, analogue gauges and full fit-up. Add $100 for the extra-longshaft 635mm (25”) model.

Engine type: Four-stroke SOHC 8-valve
Cylinders: In-line four-cylinder
Fuel Delivery: Multi-Port EFI
Weight: 206kg (lightest model)
Displacement: 2,998cc
Bore x Stroke: 102mm x 92mm
Maximum output: 150hp @ 5,500rpm
Operating range 5,000 – 5,800rpm
Shaft length: 508mm (20”), 635mm (25”)
Alternator: 60amp (belt driven)
Trim method: Power trim/tilt
Gear ratio: 1.92:1
Counter rotating: Available 
Servicing: Annually (or every 100hours after first service)
Emissions rating: OEDA three star
Warranty: Five years (recreational use)

Supplied by:
Nitro Marine
Phone: (07) 5532 5812
Email: sales@nitromarine.com.au
Website: www.nitromarine.com.au