"Average" fuel consumption?

[Paul_NY]

I realize many variables go into determining a motor's rate of fuel consumption. However, is there an "average" estimate for an Atomic 4 that is well-tuned and maintained, pushing a Catalina 27 through flat, currentless waters? (I realize the answer may very well be, "Fill up the tank, check the time, and drive it.)

Paul

[Don Moyer]

Paul,

Your question is not as difficult to answer as you might think.

An Atomic 4 in reasonable condition (compression 85 psi or above, clean carburetor, and good ignition) will average approximately 1 gallon per hour. A reasonable range would be from 0.75 to 1.25 gallons per hour.

A few of our intracoastal cruising customers report being able to lean out their engines to approximately 1/2 gallon per hour after installing an adjustable main jet (http://www.moyermarine.com/cgi-bin/shopper.cgi?preadd=action&key=FCAR_07_58) in their carburetor.

Best regards,

Don Moyer

[marthur]

We run an A-4 in our '77 C-27 in Lake Michigan. Having moved the boat some relatively long distances in calm winds and flat water we can confirm that Don's estimates apply quite well to the C-27.

If we move at hull speed (around 6 knots) we use 0.75 to 1.0 gallons/hour, higher if moving up wind in rougher conditions. However, we routinely get 0.5 gal/hr if we cruise between 5 and 5.5 knots. Our procedure is to bring the boat up to speed (5.75 knots or so) and slowly and incrementally reduce rpm until the speed drops 1/4 knot or so. Although I know about the power requirements for displacement hulls, I am always surprised by the amount of power we can pull off without greatly effecting the speed.

Don't forget to keep it tuned for best economy!

ma