5 Reasons Outboards Are Here to Stay
Are outboards poised to become the preferred power choice for midsize cruisers and passagemakers? Why not?
The first outboard motor I ever owned was a 7-horse McCulloch, which gave me decent service until one day, for no apparent reason, it seized—unfortunately when I was a couple of miles out in the Pacific. The post-mortem verdict, which I refused to accept, was that I had erred in mixing the gasoline and oil.
Thereafter I owned a string of Mercurys and Johnsons that performed as a boater in the ’70s would expect: They started hard, flooded frequently, regularly fouled spark plugs, and smoked like a mosquito-abatement truck. In those days the blue haze was welcome however, being a sign that the bloody thing was at least running.
Things got incrementally better through the ’80s until the EPA came to the rescue. Yes, the universally despised EPA handed down emissions regulations that drove a stake into the heart of the noxious and obnoxious conventional two-cycle marine engine. (They also killed the two-cycle Detroit Diesel.)
Although it may sound like I harbor less-than-warm feelings for outboards, I most assuredly do not. I have owned three four-strokes, including my current 100-horsepower Yamaha, and all have been model citizens: quick-starting, smooth-running, quiet, fuel efficient, smokeless, and reliable as an Army mule.
Not only am I fan of outboards, I am a proponent. I believe that the modern outboard is, or should be, the best power option for many boaters, and in many ways superior to inboards, stern drives—even pods. After all, with rare exception, the outboard motor is the only engine designed from the ground up for marine use. Don’t buy it? Just look at how the modern outboard stacks up.
Weight: On a horsepower-to-weight ratio basis, outboards cannot be beat. You probably already know this intuitively but here’s a graphic example: Mercury’s 300-horsepower Verado Pro four-stroke is listed at 635 pounds, or 2.12 pounds per horsepower. Mercruiser’s 315-horsepower 5.7 MPI ECT stern drive engine alone weighs 885 pounds. Add to that the lightest Mercruiser drive unit, the 88-pound Alpha One, and you have a total of 973 pounds. or 3.09 pounds per horsepower.
Fuel efficiency: The four-cycle outboard uses the same basic combustion process as any four-stroke gasoline engine, so its brake-specific fuel consumption (bsfc), the metric engineers use to measure engine efficiency, falls within the same range: 0.37 to 0.45. (The number represents the number of pounds of fuel to produce one horsepower for one hour.) I have not been able to determine the bsfc for the Evinrude E-TEC outboard, a direct-injection, two-stroke design, but anecdotal information indicates it is comparable to that of the typical four-stroke gasoline outboard. Yes, turbocharged diesels are more efficient: their bsfc range is 0.30 to 0.35.
But it’s important to remember that fuel efficiency is inextricably tied to weight; a lighter engine could theoretically compensate for an efficiency deficit by virtue of having less total weight to push through the water. The 300-horsepower Cummins weighs roughly 2,000 pounds, less exhaust system and marine gear.
Maintenance: Outboards generally require about the same maintenance as inboard gasoline engines and less than diesels (although diesel maintenance is more costly). But they are much easier to work on: A good boatyard can do a total outboard engine swap in a couple of hours, where the job for a diesel is measured in days.
The outboard’s tilt mechanism also means that when it hits an underwater object, it can often kick up before significant damage occurs. Normal propeller maintenance may require simply tilting the outboard rather than hiring a diver or a Travelift.
Space efficiency: Horsepower for horsepower, outboards are smaller than other marine power options. But size isn’t the main issue. What counts is where the space is that the engine occupies. Since the outboard is on the transom or abaft it, the engine in effect occupies unused space.
Look at it this way: One of the great advantages of pod drives is that the engines sit farther aft, allowing designers as much as 10 feet more interior space to play with. Imagine what they could do if there were no engines inside the boat.
Cost: A cost-per-horsepower comparison is impossible because OEM engine pricing is such a closely held secret, but we can say that outboards are less expensive than diesels and pods and probably close to that of stern drives and inboards. Compare cost per knot and outboards have the edge.
Now you’re probably asking, “If outboards are so great, why are they mostly just in small boats and center consoles?” The answer is part prejudice and partly because few designers have come up with a compelling midsize cruiser based on outboard power. Will outboards ever be able to supplant inboards? They just might.
This article originally appeared in the November 2015 issue of Power & Motoryacht magazine.