My C&C 38 has an A4 with a 2:1 reduction and a solid 16x10 prop. Fuel
Burn is just over 1 gph at 2500-2750 rpm's.
James T.
Delaney
Oriental, NC
On 7/14/2018 10:57 AM, Dennis C. via CnC-List wrote:
I had AT4 in Touche', 35-1, for a few years. Had Martec folding 14x5P
prop. Fuel economy was about 1 gph for usual conditions.
If you were motoring into wind and waves, you were more than likely
"making bubbles". That is, in order for you to get to the full
horsepower of the AT4, you were near max rpm, 2500-2800. Your AT4 is
probably a 1:1 transmission. Your boat speed was slower therefore
your prop was probably cavitating quite a bit due to the high prop
rpm. The resulting inefficiency drove your fuel usage up.
Diesels are usually reduction drives, usually about 2:1. Therefore, a
diesel running 2800 rpm has a prop speed of about 1400 rpm. Diesel
drives are pitched at 12-16, give or take. That, and a flatter torque
curve, is why diesels are better for punching into waves.
Dennis C.
Touche' 35-1 #83
Mandeville, LA
On Sat, Jul 14, 2018 at 9:29 AM, jay hackney via CnC-List
<cnc-list@cnc-list.com <mailto:cnc-list@cnc-list.com>> wrote:
Hello colleagues
Filled with gas for the Atomic 4 in Port Whitby Canada Day and
sailed back to Toronto. Wind out of the West and tight timeline
meant we had to motor against the wind and waves for 2.5 hr. That
would be relatively “hard” motoring at 4-5 knots. Since then I’ve
motored about another 3/4hr for a total of 3.25 hours, again at
about 4.5 knots. Filled with gas again the other day to measure
gas consumption and got 7.9 litres per hour, or 1.8 gal per hour.
I’ve got a 2-blade folding prop (which, by the way, make reversing
difficult - in the sense that there is no quick stopping).
Does that seem normal?
Online research seems to go from 0.5 to 2-3 gal per hour.
Anyone with an A4 on a C&C34 with a gas consumption comparison out
there?
thanks
Jay Hackney
Windblown
Toronto
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