Motoring DF 35

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EarthBM
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Motoring DF 35

Post by EarthBM »

Will be taking my DF 35 down the West Coast next week (~1200 Nm) with Steve B. + 1 other. The first day (Saturday) looks like we may have very light winds getting to the ocean through the Straight of Juan de Fuca. Combined with timing the tide motoring may be the best option for the first 12-18 hours.

Quorning specs say 80 liters in the diesel tank. Last weekend I had 9 liters on the gauge, filled it up to the brim but only got 15 gallons in (53 liters). For the total of 9+53=61 liter. Does that mean the gauge will show 0 while there is about 20 liters left in the tank?

What kind of GPH use should we expect at, say, 6 knots of water speed? Does it differ much from 5kt or 7kt speeds?
Ivan -- DF 35 #29 "Lykke"
Double Horizon
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Post by Double Horizon »

I don't think you can depend on the gage to be accurate. The capacity of the tank is usually located on a plate stuck to the tank, and I think you can rely on that. But you also can't count on whether the fuel pick-up is close to the bottom (it's usually a good practice to make the fuel pickup about an inch above the bottom so it isn't as likely to suck up sediment and water).

The way to test it is to bring an extra jerry jug (or two) with you and run it down until it runs out of fuel, then refuel and you will know how many gallons from true empty until full. (Obviously, you want to pick a time/place when running out of fuel will not present a danger).

As for fuel consumption, I don't know for your boat. A general rule is Diesel engines consume about 1 gallon per hour for every 18 hp used. You can estimate the number of gallons consumed per hour by multiplying horsepower used by 0.055. The key is the word "used". If you don't use full power you will burn less fuel.

As points of reference, my DF 1000 averaged about 0.6 GPH with the 20 hp engine, and my DF-1200 averages about 1.22 GPH with the 57 HP engine. That's actual use calculated by using the hour meter and gallons between fill-ups, so there is idle time, harbor time at slow speed, etc. along with cruising time.

Also, if you are running below "hull speed" there is less resistance through the water, and that can improve MPG.
Larry - Former Owner DF-1200
Double Horizon
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Post by Double Horizon »

Another thing to consider, is that if your tank is narrower at the bottom it will cause the gage reading to go down faster as the tank empties.
Larry - Former Owner DF-1200
EarthBM
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Post by EarthBM »

Thanks Larry. I guess this gives me ~130nm full tank range (interpolating about 1gph from your numbers for my 30hp motor, times 6kt speed at 2/3 power, times 22 gallon tank). I will try to keep track of this on the trip and will report back
Ivan -- DF 35 #29 "Lykke"
Double Horizon
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Post by Double Horizon »

EarthBM wrote:Thanks Larry. I guess this gives me ~130nm full tank range (interpolating about 1gph from your numbers for my 30hp motor, times 6kt speed at 2/3 power, times 22 gallon tank). I will try to keep track of this on the trip and will report back
Your numbers are probably good for planning purposes, but you may do better than that at 2/3 power because unless you have a headwind, the DF35 is an easy boat to push.
Larry - Former Owner DF-1200
Double Horizon
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Post by Double Horizon »

PS - have a great trip!
Larry - Former Owner DF-1200
Steve B.
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Film at 11

Post by Steve B. »

June 11th that is...

I'll post some pics.
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