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FloScan and Prop Analysis Solve Fuel Mystery.
 

FloScan and a computerized propeller analysis system solved the nagging problem of unbalanced fuel consumption by the diesel engines of a 44-foot motor yacht. The starboard engine of the GERRI-L, a Tollycraft equipped with 6V-53TI Detroit Diesels, had begun using 20-25% more fuel than the port engine. There were no unusual vibrations to indicate a bent prop, and a diesel mechanic confirmed all injectors were operating properly. Yet the Series 9000 FloScan fuel flow system aboard consistently showed higher fuel use on the starboard side, which was also confirmed at the fuel dock.

Even when the boat was hauled for bottom paint, there was no apparent damage to either prop, especially the starboard wheel that was using the extra fuel. The cutlass bearings were checked and all was well. Preparing for a summer cruise into Washington and British Columbia, skipper Bill Chevalier, of Portland, OR, talked with his long-time prop shop, Sheffield Marine Propeller, Inc. Walt Sheffield, who works on everything from outboard props to tugboat screws, suggested starting withthe boat’s spare props, a set of 26x26 Nybrals.

The spares were checked on Sheffield’s Hale Measurement Recording Instrument (MRI), which checks the pitch, rake, spacing, geometry and camber. The spares checked out to be within specification. Chevalier had the boat hauled and the spares put on, then took the original props from the boat back to Sheffield. As the MRI printed out its findings, Chevalier told Sheffield, "There has to be a mistake. My FloScans don’t lie," he said. The MRI said the starboard prop was within spec, but the port propeller had a blade that was far out of the norm. This was just opposite what Chevalier expected to discover, since the extra fuel was being burnt on the starboard side. Sheffield pointed out that the type of damage to the port prop actually had reduced its pitch in the water, letting the starboard engine carry more load and thus use more fuel.

During the summer cruise, GERRI-L’s engines settled down to a mere 1–to-2 percent variance on fuel usage. Chevalier depended fully on the FloScan for trip planning and for preventing spillage at the pump. After his initial top-off, Chevalier used the FloScan totalizer to fill each 200-gallon tank to within five gallons of indicated use. Then, at subsequent fuel stops, he added precisely the totalizer gallons, knowing he would always be just five gallons short of overspills.

The system installed on Bill Chevalier's boat is the Series 9000 GPS Interface model which displays Engine Hours, RPM’s, Gallons Per Hour, Gallons Used, and Nautical Miles Per Gallon. This system totally eliminates the need for calculating and plotting a fuel/speed curve since the boat operator can reach optimum fuel efficiency by simply changing the throttle position successively until the instrument’s MPG reading peaks. Furthermore, the system pays for itself many times over with the fuel savings obtained by running at the peak efficiency point at all times.
 


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