What a successful summer cruise!
In nearly seven weeks under way and more than 700 miles traveled, Quadra encountered only 40 minutes of rough water. It was hidden, waiting for us, in the center of 18-mile-wide Georgia Strait in southern British Columbia, on an otherwise calm crossing.
Better yet, by slowing engine rpms from the traditional 1,800 to 1,600 we reduced fuel consumption significantly – from the historical 4.8gph to 3.3gph. Measured in miles per gallon, we also did well – stepping up from the usual 1.5 to 2.
My math skills are feeble, but some time with a calculator showed that fuel consumption dropped about 30 percent as the result of slowing engine speed 11 percent.
Average speed dropped, of course, from 7.5 knots to 6.6. Slowing did not diminish the pleasure of cruising for one moment.
That’s putting a choke hold on dollars flowing to oil speculators.
My personal challenge before the cruise began was to achieve 7 knots without exceeding 1600rpm. We missed the goal slightly, but we often ran slower when a beneficial current would give us 7 or more. Those gains often are illusionary along the Inside Passage because for every current going your way there’ll be an opposing flow a few hours ahead, or just around the next point of land.
I bought fuel in Canada once, to get some idea of change in the burn rate. It cost $5.80 a gallon (after converting liters to gallons and considering the exchange rate and including sales taxes). Fueling in Friday Harbor, Washington, near the end of the cruise, I paid $4.70 a gallon plus 8 percent in taxes, or $5.08.
One of the serious issues inherent in slowing engine speed is whether the engines will maintain proper temperatures and pressures. With my Ford Lehman 120hp diesels, that appeared to not be a problem when reducing engine speed to 1600.
I use a hand-held remote laser thermometer to check key points on both engines. The readings seen at 1600 were nearly identical to those noted at 1800. Gauges at the helm showed no change either, with oil pressure steady at about 35 psi and temperature a degree or two below 180.
The hottest spot in the cooling system at was at the base of the expansion tank, where it mounts on the block. I measured 175 degrees at 1800 and 1600rpms, so I would judge the temperature inside was about 180.
Oil temperature is harder to measure from outside the engine. I focused the thermometer on the outlet through which oil exits the block enroute to the filter and cooler. At 1600 and 1800 rpm it was steady at 160 degrees; the oil probably was several degrees hotter inside the engine because the port was exposed to cooler air. That temperature falls within what is considered the ideal temperature range for lubricating oil – from 160 to 200 degrees.
Transmission temperatures changed little, showing 106 to 115 degrees at those speeds. The short piece of exhaust pipe between the manifold and the water-cooled exhaust riser can measured 305-314 degrees at 1800rpm and about 265 degrees at 1600rpm.
At 1400rpm, the engines cooled. Coolant temperatures dropped to about 160 degrees and lube oil temps fell to about 140 degrees. After running at 1400 while going with the flow, I always pushed the throttles ahead and brought engine speed to 1800 for 10 or 15 minutes before resuming travel at 1600.
Another benefit was a reduction in engine noise. I did not have my decibel meter aboard, but the difference was noticeable.
This season’s performance was compared to a trip to Southeast Alaska in 2006 when Quadra traveled 2,100 miles and clocked 282 hours of engine operation, burning 1,388 gallons of diesel. That year, fuel cost $4.20 in Canada and $3 in Alaska.
In the trip just ended (reluctantly), we logged 715 miles and burned 355 gallons of fuel. Even at 6.6 knots, every mile was a treasure.