Product Spotlight | Mercury 150 4-Stroke Nuts & Bolts
Article written by Bill Gius
If you have a fiberglass or aluminum outboard powered boat, you don’t want to feel vibration from your engine at any RPM range. The more horses you hang on the back of the boat, the more your outboard weighs. The more weight that teeters on a hinge, so it can be trimmed and be tilted, the more engineering that has to go into the design of every component of the engine’s transom bracket. At around 455 pounds, the new Merc 150 is “light” for its horsepower. Between you and me, 455 pounds isn’t what I’d call “light”. I’m not sure how many of my close personal friends and myself it would take to lift 455 pounds but the 150 is lighter than comparable Suzuki, Yamaha or Honda’s by 19-23 pounds.
Inside the engine is a very violent place. All those explosions cause the pistons to move along pretty quickly. And they have to come back to get banged on again; and again and again. No matter how good the engineering and manufacturing of the actual engine part of the outboard, there will be some vibration that will escape the block and try to get transmitted to the parts of the outboard that hold it to the back of your boat. The drive train, from the power head all the way to the propeller tips, also generate some vibration. Engineers work to attenuate (reduce) as much of that vibration all along the system but all those gears meshing together also add to the opportunity for vibration. Modern engines and drives are designed tremendously better than the same horsepower engine from just 15 years ago. Four stroke engines have further advantages in reducing vibration and noise because of the inherent design in an engine that has four instead of two combustion “cycles”.
All outboard engineers understand how vibration travels too. The Merc engineers and marketing folks thought about that and came up with a pretty neat name for their engine mounting system. They call it the “Focused Engine Mount” system. Merc could have used an engine mounting system and transom bracket from one of their other outboards. Those designs have held up to dozens of years of real world use on hundreds of thousands of engines and well over 300 horsepower outboards. They’ve worked just fine. But this is a totally new design all around.
Hidden in the midsection of the engine (the part below the engine block and above the gearcase) is this focused mount system. They’re mounted to attenuate the focused forces and vibration of the engine at the key load points. The mounts are also kept from the effects of heat and any dripped oils that could damage or change the characteristics of the rubber in the mounts. The composition of the rubber and how it’s fastened to the mounts allows the rubber to be compressed at different rates. At lower RPM’s where you’re apt to feel more true engine vibration, the rubber is “softer”, because it’s not as compressed. At higher RPM’s when you’re up and running it’s more compressed and more firm to better hold the engine in line with the boat (that keeps it from wobbling back and forth and helps keep you going straight).
All that is attached to the engine side of the transom bracket which incorporates the trim and tilt hydraulic pump and ram.
On some transom brackets the hydraulic pump is mounted outside the bracket. On the 150, it’s inside the bracket, protecting it better and making for a more compact system. Even though this engine weighs in at 455 pounds, it uses a single hydraulic ram for trim and tilt. Some other engine use two shorter rams for the trim and a single longer cylinder for tilt. Again, this makes for a more compact and yes, less costly system.
In this and the two previous articles we’ve taken a good, introductory look at the new engine. Mercury hasn’t told me the pricing yet but it’s now available and they have suggested it’s going to be more competitive than other makes. That will be important but durability, performance and fuel economy will also play into the engine’s total cost. Four stroke’s suck less fuel than two cycle engines; they don’t have the power curve of a two stroke and durability is an argument I don’t want to start but this engine is worthy of consideration when you’re shopping for pontoon, fishing or cruising power.
(Bill Gius is a three-plus decade marine industry veteran with extensive, hands-on accessory, boat and engine experience. Bill has been working with iboats.com for six years to help manufacturers and dealers use iboats’ online marketing, advertising and lead generation services. Bill can be reached at 800-869-1686 x199 or firstname.lastname@example.org.)