Motoring Range, CD31

[Dean Abramson]

Has anyone out there figured out the approximate number of hours a CD31 can motor on one tank of fuel? Let's assume motoring at around 80% of max revs.

I have the Universal M25 and a 20 gal. tank, which I assume most/all 31s do.

Dean

[JWSutcliffe]

Dean:

I figure on 1/2 gpm with mine at 2200 rpm, which works out to 40 hours max from the onboard tank. Actual fuel burn is a bit less with typical usage, since we use lower rpms going into and out of the harbor. I have two 5 gallon jerry cans, but normally only carry one if we are going out for a week and havent yet actually used it.

[Ray Garcia]

Same way my dad used to figure it out when he needed to fill the tank on the van. The fuel gauge was broken and my dad being the frugal person he was decided to track his mileage and fuel consumption manually. He would record the mileage, and the amount of fuel (gallons) he would purchase. Of course he ran out of gas once. That created his baseline of, you guessed it, empty-tank.

Fill the tank, record the gallons pumped and the hours on the engine gauge. Motor around keeping track of your speed at the desired RPM's and make note of that too. At about approx. 1/2 tank, fill the tank again, and record the data again. Your first calculation should give you a rough estimate of gallons per hour and how far you can make it on a full tank. The more times you complete the data/calculation cycle the more "accurate" your result will be. Though as you know there are plenty of variables that could skew your results. Tidal current, wind, waves, and bottom growth will affect your fuel consumption.

Note: If you do not know this already or for other readers; subtract about a gallon or two from your tank. You will never use it. Why? you ask. The fuel pickup tube does not reach all the way to the bottom of the tank. If it did the fuel system would vacuum up all the crud and water that may be in the tank. Not good. The pickup tube is about 1 or 2 inches off of the bottom. If I let the tank go down to a little over a 1/4 and the going gets rough the motor will stall due to ingesting air in the fuel lines. If the forecast looks snotty I try to remember to fill the tank before heading out. Of course I have forgotten and have had to bleed the engine every time she would stop.

[JAS]

Loon (CD31 with universal 25) came with extensive notes from previous owner. He indicates that she runs 3-3.5 hrs/gallon (60 hrs/full tank) and he always ran at 1600-1650 RPM (5-5.3Kt in calm seas). All other notes have been accurate, so I think this should be a reasonable estimate.

[Phil Shedd]

Dean

I use 8 hours of motoring per quarter of a tank but to be on safe side say 30 hours motoring per tank full 21-2200 rpm. This has work out well. Sometimes going to Maine we have to motor a lot to get down east. The wind at that time of year is right on the nose ie out of the south west.

Phil

[Thomas Kyasky]

Dean,

I have a Beta Marine 20hp with a 3 blade maxi-prop and at 2800 rpm in calm seas with a light head wind I make 5.5 knots and use about a 1/2 gph. If I have to motor all day (8 to 10 hours) on average I will use about 5 gal. in variable but not extreme wind and sea conditions.

Fair Winds,

Tom