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Fuel saving tips
Bowgus wrote:
And use that trim control for optimum speed/rpm combo. Aha! I would have overlooked that, thanks. Your point has been blatantly hijacked and included in my rough draft. :-) Don't be so Fuelish! Holy hydrocarbons! All the dead dinosaurs currently being pumped at the local fuel docks must surely have been the thoroughbreds of their day. As the summer cruise season gets underway, gas and diesel prices are high, yi, yi, yi, er than we've ever seen, (if inflation isn't factored into the equation). What's a boater to do? Fortunately, we have some realistic choices that go well beyond staying ashore and moping. Without suffering major expense or inconvenience, almost everyone can make some simple adjustments and systems checks that will reduce fuel costs this summer. In some cases, the savings will prove significant. Boaters should always be careful to maintain a nice, clean bottom. Lack of attention can result in an embarrassingly "hairy" surface, further plagued by unsightly, crusty organisms clinging to formerly smooth, unblemished surfaces. It it's been a while since the last careful examination, it may be time to take your bottom (and the boat it's attached to, of course) to the nearest boatyard for inspection, correction, and preventive maintenance. The "beard" of seaweed and the hitch-hiking barnacles can retard a boat's progress through the water and decrease fuel efficiency as a result. The energy developed by burning fuel aboard a powerboat is ultimately transmitted to the water by the prop. Boats fitted with a propeller pitched too aggressively or too large in diameter will be "lugging", and the over-propped condition will keep the boat from ever reaching the manufacturer's rpm rating. If the engine is running at a wide open or well open throttle and not achieving its potential speed, some fuel is being wasted. If a boat is equipped with an undersized propeller, it will easily reach or exceed its full rpm rating but will not convert the engine speed into boat speed with adequate efficiency. Boaters who have been "putting up with" improperly sized propellers may find this a compelling year to make the correction. Engines that are running efficiently burn less fuel. Is it time for fresh sparkplugs or other ignition components on a gas engine? Are the injectors overdue for service on a diesel? These and similar preventive maintenance chores can't be postponed forever, and doing the work prior to setting off on an annual vacation cruise will allow the immediate fuel savings to help defray a portion of the cost. Prepare to lighten ship! The smaller the boat, the greater the difference an extra thousand pounds of "stuff" will make when operating. Basic safety gear and spares should remain aboard, of course, but a spike in the cost of fuel is as good an excuse as any to go through lockers, lazarettes, etc, and review the inventory. Most of us will be surprised at the amount of seldom or never used, (sometimes even completely forgotten), stores, supplies, tools, and personal belongings stowed aboard. Don't boat "upstream" when avoidable. In most of our local tidal waters, there are only the briefest periods when the current is truly slack. Prudent planning and timing of a cruise can make a significant difference in net speed over ground, (and therefore actual fuel efficiency). Displacement boats realize more dramatic benefit from the advantageous use of currents than planing boats. An eight-knot boat bucking a three-knot current will achieve a net five-knots, while the same vessel running with a three-knot current will be logging eleven-knots SOG, (more than twice the speed with the same fuel burn). And last but far from least, slow down! (But perhaps not too much.) The two most efficient speeds for typical planing hulls are pure idle, and the speed at which the boat rises over the bow wave to assume a planing attitude. Backing off the throttle to where a boat falls off plane will reduce the gph fuel consumption, but can easily reduce the speed so disproportionately that the nmpg is actually less at the lower speed. Once a vessel has achieved planing status, additional throttle will often burn significantly more fuel to achieve only relatively modest increases of speed. Judicious use of trim tabs, when so equipped, can often help a boater achieve or maintain plane at a slower engine rpm. Even if it isn't practical to clean the bottom, tune or service the engine, correct an improperly specified propeller, remove excess weight for the boat, or plan cruises to take advantage of favorable currents, many of us can realize significant savings merely by reviewing our customary cruising speeds. Cruising a bit slower may sound almost heretical to many boaters, but let's examine a real life example of the type of efficiencies that can be realized. Douglas Silvestri, of Port Orchard, Washington, kept careful fuel consumption records on his 36-foot Uniflite equipped with twin 460 gas engines and Flo-Scan fuel meters. Silvestri recently traded for a different boat, but he kept his old records. "At 2700 rpm, I would make 14.1 kts in the Uniflite. My combined fuel burn at that speed, for both engines, was 14.2 gallons per hour, or almost exactly 1nmpg." "By slowing down to 2000 rpm, my speed dropped to 10 kts, but my fuel burn was reduced to 8.2 gph, according to the Flo-Scans." Doug's fuel efficiency, on a nmpg basis, was roughly 25% better at 2000 rpm and 10 kts than it was at 2700 rpm and 14. Doug actually got reasonably decent fuel economy from the twin 460's in his Uniflite, many similar and larger boats use significantly more fuel per hour and a decrease in speed could result in even more dramatic savings. Here in the Northwest, many boaters would hardly notice the difference in Doug's two speeds, but most would appreciate the difference in fuel costs. A 250 nautical mile summer vacation cruise would require 25 cruising hours at 10-knots, or just under 18 cruising hours at 14.1. If the 250 nautical miles were logged over ten days, the average running time per day would only be 42 minutes longer at the slower speed. Eighteen hours at 14 gph would burn 252 gallons at the higher speed, while 25 hours at 8.2 gph would burn only 205. By spending an extra 42 minutes per day on the water, (and isn't that what boating is supposed to be about?) Silvestri's old boat would use 47 fewer gallons on that typical, but hypothetical, NW vacation cruise. At $2.80 a gallon, that 47-gallon savings would reduce the fuel costs by $131. One-hundred-thirty -one dollars isn't a lot of money in the grand scheme of boating expenses, but its an amount that almost anybody would stoop down to pick up if it were laying unclaimed on the dock . For many of us, that much or considerably more almost certainly is. |
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