mercury's new 150 hp fourstroke
- vol. 14 # 5
by Chris Kourtakis
When Mercury Marine set out to design and build its all-new 3.0 L four-cylinder in-line 150 hp FourStroke, the company asked its customers what they needed, what they wanted and what the engine should do. The end result is an engine that Mercury touts as being the lightest, most fuel efficient and durable engine in its class.
I had a chance to test the new 150 hp at the recent Fort Lauderdale International Boat Show in October at the Mercury Marine media event. One of the first things I noticed was the engine’s size. The entire profile of the 150 hp is not what I was accustomed to for a 150 hp outboard engine. In fact, it resembled more of a 75 hp or 90 hp as the entire engine is visibly smaller than other engines of similar power.
Tilting the engine out of the water, I knew that Mercury had designed this motor from the skeg up and I wanted to see the changes they have been bragging about. I immediately noticed the large gear case is longer compared to other outboards in this range. In fact, the new 4.9-inch gear case meets all of the durability requirements of a 300 hp class outboard.
There’s also a beefier 1.92 gear ratio inside the casing to ensure added durability. I instantly thought this gearcase was going to affect overall speed, but I shouldn’t have let the size fool me. In fact, during in-house testing, Mercury conducted extensive Hydrodynamic testing, which resulted in better hydrodynamics. The gear case design also provided excellent lift, which holds more of the boat out of the water, thus providing better performance at mid- to top end speeds.
I took the cowling off and as I looked over the engine’s components, the 60-amp alternator is a marine-hardened, automotive-style system, which means it’s an external unit driven by the crankshaft via the serpentine belt. This means the system is fully regulated and supplies current only when it is required. It also recognizes when the battery voltage drops below 14.2 volts and engages the alternator to re-charge the batteries.
The automotive-style alternator produces more than 67 percent of its 60-amp output at only 1,000 RPM, which allows it to charge batteries quickly without having to run hard, or more importantly, burn a significant amount of fuel. When the alternator is not charging the boat’s batteries, it “free-spins” preventing unwanted heat buildup under the cowling.
Another unique design are the engine mounts. They are located further from the power head to help reduce mount temperatures and increase the durability of the mounts. Additionally, they are angled to significantly reduce vibration transmitted to the boat at all points while running under load, which also simplifies servicing as technicians don’t need to remove the power head.
The test ride of the 150 hp was performed on the ICW and rigged to a 2011 Boston Whaler 190 Montauk, weighing 1,900 pounds with a ¾-tank of fuel at 55 gallons and three people on board. The 150 was spinning a 17-pitch Enertia Mercury propeller.
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