|Bore x Stroke
|4.0 x 3.6|
|Fuel/Air||Naturally-Aspirated Multi-Port EFI|
|Ignition||ECM digital inductive|
|Alternator Output||60 Amps|
|Dry Weight||455 Pounds|
|Gear ratio||1.92 to One|
|Warranty Term||Three Years|
Dubbed the 150 FourStroke this naturally-aspirated engine joins two other Mercury 150-horsepower outboard motors: Namely, the supercharged Verado 150 and the Direct-Injected 2-stroke OptiMax 150. So why does Mercury offer three radically different technologies in the same horsepower rating? The answer is as simple as the sea is salt. The bass boat crowd prefers lightweight, two-stroke technology with lots of low end torque, motors like the wildly popular OptiMax Pro XS. While offshore boaters prefer the technology and mind-numbing performance of the supercharged Verado. The newcomer, 150 FourStroke offers a lower-priced alternative to both of these engines, an offering that gives up nothing in the way of performance. And the price is right.
I already know what you're thinking, and rest assured, the introduction of this lightweight, lower-priced four-stroke does not signal the end of Mercury's Direct-Injected, 2-Stroke OptiMax.
Mercury's 150 FourStroke powerhead is founded upon nothing less than a 3.0 liter In-Line four-cylinder block. Know that typically that's the displacement of a 200- to 250-horsepower outboard. True to the timeworn axiom that reminds us there is no substitute for cubic inches, 150 FourStroke's super-sized displacement pays big dividends in low end torque.
When rigged with 150 FourStrokes big, heavy hulls will more easily climb over their bow wave and onto plane and acceleration will send a pleasurable shiver up and down your spine. Admittedly, the thrill ride is not quite as pleasurable as a supercharged Verado, but it is still a rush. The massive 3.0L displacement will mimic the performance of many two-strokes, while at the same time providing excellent fuel efficiency. Even though it's a big block this outboard weighs just 24-pounds more than the 2-stroke 150-hp OptiMax.
The cylinder head is populated by a single camshaft and just two valves per cylinder. Simply put, with its big block displacement the Mercury 150 FourStroke doesn't need the extra weight and complexity of a second camshaft replete with timing chain and two additional valves per cylinder. The intake and exhaust valves are actuated by finger roller followers, technology derived from Formula One racing. With them in place this engine does not require the hassle and expense of periodic valve-lash adjustment (micrometer and shims), as do other four-stroke outboards.
Look carefully at the powerhead and notice it has been rotated 11-degrees to port, a modest rotation that made room for a compact scroll shaped intake manifold. The snail-shell-shape effectively lengthen the intake runners which in turn pumps up low end torque.Know that when compared to 2-strokes, 4-strokes make less torque at lower rpm. The scroll manifold and big cubic inch displacement obviates that shortcoming.
One clever innovation is the QR code stuck on the motor. Scanning the symbol with a smartphone calls up Mercury Marine produced YouTube videos that show step by step exactly how to change motor and gear case oil as well as other DIY tasks.
Speaking of which, I like the new crankcase sump fitting that opens with a half turn of the wrench a lot like a brake bleeder fitting. With a drain hose attached you can change engine oil without spilling a drop or dirtying your fingers. As for the fuel filter, to change it just grab its big yellow parachute ripcord-like handle and pull. In other words, you don't need tools. Neither will you need a grease gun, as the motor is permanently lubricated.With this news a disconsolate Oscar Zerk, inventor of the zerk fitting,is probably spinning in his grave at 5500 rpm.
Rigging is very easy,boasting compatibility with standard mechanical cables, dual cable or hydraulic steering compatibility, and the ability to run on either standard analog or full SmartCraft instrumentation straight from the factory. All of the connections under the cowl (throttle and shift cables, data harnesses, et cetera) are easily located and accessed for quick, intuitive, and hassle-free rigging. In fact, this engine was designed to be easier to rig than any other 150. It is compatible with standard mechanical throttle and shift, dual cable steering, hydraulic steering, and even full electro-hydraulic power steering on twin-engine installations. Itdisplays engine data with basic analog gauges or full SmartCraft digital instrumentation without having to swap out any sensors or senders. It is also compatible with Mercury's innovative Big Tiller system.
Repowering is quick and easy.A smaller profile and low tilt arc make the 150 FourStroke a perfect choice for boats with small transom wells, enclosed engine covers and poling platforms.And thanks to its modest dimensions and low curb weight, the Mercury's 150 FourStroke is a tantalizing possibility for re-powering older hulls with transoms not originally designed to accommodate the inherently heavier weight of a four-stroke engine.
Finally, the new 150 FourStroke is built at Mercury's headquarter facilities located in Fond du Lac, Wisconsin and is protected by a three-year limited, non-declining warranty.
© Copyright Timothy P. Banse
Marine Engine Technician, Timothy Banse, has published articles in Popular Mechanics, All Chevy, Pickup Van &4-Wheel Drive, Mecanica Popular, Motor Boating, Yachting, Mar y Vela and many other magazines and newspapers from around the world. He writes about cars, trucks and tow vehicles as well as automotive- and marine-engine technology.