September 21, 2011
How to get more miles out of those pricey gallons.
Take the sting out of fill-ups by moderation your speed and keeping your hull clean.
So, how are things at the gas docks for you these days?
If you're like most boaters, you may be having second and third and fourth thoughts about buying that big V6 outboard. Triple power anyone? Not!
At $3 a gallon and more, boaters are clearly going to want to cut back their gasoline use.
The good news is there are ways to neatly double your fuel economy—which is about what you need to do to make up for the fact that gas now costs exactly twice what it did for years.
First, it's all true about slowing down. Having run fuel efficiency tests on literally hundreds of outboards over the last 20 years, I can report with certainty that many boats get way better economy at 3,500 to 4,500 rpm than they do at 5,000 rpm and more. The difference can literally be 25 to 40 percent.
For example, a Whaler 320 Outrage with twin Merc Verado 250 four-strokes did 17.8 gph at 3,500 rpm, delivering 21.9 mph and 1.23 mpg. At 6,000 rpm, the engines used 51.0 gph while pushing the boat 46.7 mph for 0.91 mpg—a 26 percent reduction.
A Bluewater 2850 running twin Yamaha 225 four-strokes used 16.2 gph at 4,000 rpm and 33.4 mph for a 2.1 mpg average, while at 6000 rpms these motors used 43.1 gph and pushed the boat 50.9 mph for an average of 1.2 mpg—a credit-killing 43 percent increase.
Note that this is not true of all boats. Lighter boats like flats rigs with single four-stroke or direct-injection two-strokes often nearly match their cruise economy at top end, probably because they get “jacked up” and reduce the wetted surface, the part touching the water, which cuts drag as they reach maximum trim and maximum speed. For example, a 1910 Coastal Bay I ran with a 140 Suzuki four-stroke got 6.3 gallons per hour and ran 22.6 mph at 4,000 rpm—a very economical rig delivering almost 3.6 mpg. Drop the hammer on that motor and wind it up to 6,000 rpm and the gallons per hour shot up to 12.1, but speed also went up, to 43.1 giving an almost identical 3.56 mpg.
Similarly, an Edgewater 170 with a 90-horse Yamaha four-stroke delivered 3.2 gph and 16 mph at 3,500 rpm, for an impressive 5.0 mpg. Wind that motor up to 6,000 rpm and the gph climbed to 8.6, at a speed of 39.2—the boat still delivered a very economical 4.6 mpg.
If you're paying attention, you can see that smaller, lighter boats use far less fuel than big, heavy ones, whatever the speed. So that may be something to keep in mind when it's time to trade, if the current fuel woes continue.
And you will want to bite the bullet and pay extra up front for direct-injection or four-stroke power due to their vastly improved economy over the few carbureted models still available. This didn't necessarily make sense at $1.50 a gallon but at $3.00 it does. Don't ignore the high-tech two-strokes; they deliver much more spirited performance, weigh less, and offer almost identical fuel economy to the four-strokes.
How you run your boat can also make a difference. For those running big boats offshore on the East Coast, taking advantage of the north-flowing Florida Current (popularly known as the Gulf Stream) can help on north-south legs. Run close to the beach where there's no current when you're going south, but get out over the blue water when you're going north; you'll gain a 2 to 4 mph boost in speed at no added cost in fuel on the northward legs thanks to the flow.
And, of course, you'll want to keep your motor tuned up, the bottom of your hull clean, and also get rid of excess weight in the boat, particularly weight near the bow. Trimming the boat right helps.
If you're a troller, you can gain a huge benefit by adding a “kicker” motor on the transom, linked to the steering of your main motor. A little 10 or 15 horse will burn practically no fuel while you're towing baits, and it has the added advantage of allowing you to slow down well below idle speed on that big V6—a big plus for live baits.
In short, higher gas prices hurt, any way you slice it, but it's possible to manage the pain with a bit of planning and common sense while we wait for the prices to return to some semblance of reason. FS