I don't think fuel economy is relevant in the same way it is for a car. I hardly ever buy more than 150 gallons of boat gas a year, so even free diesel wouldn't pay for an engine swap. What does matter is physical space. The previous Coquina had a 4-107 Westerbeake diesel and the same size fuel tank the present Coquina has, but could go twice as far with the same size tank. I would not have got another A4 if my projected use of the boat in the near term involved a lot of offshore passages.
Joe Della Barba Coquina C&C 35 MK I From: CnC-List [mailto:cnc-list-boun...@cnc-list.com] On Behalf Of Russ & Melody Sent: Sunday, February 02, 2014 7:47 PM To: Dennis C.; cnc-list@cnc-list.com Subject: Re: Stus-List The real reason to switch from an AT4 to a diesel Hi Dennis, A comment regarding "Increased fuel economy? - Maybe" With both engines properly maintained... the only situation of not having increased fuel economy is if acquiring gasoline at nearly half the price of diesel. The reasons are twofold, diesel engines are inherently more efficient due to higher compression ratio and diesel fuel is 15% heavier than gasoline so each unit contains more hydrocarbons. A third factor in sailboat fuel efficiency is the size of wheel you swing in the water. As you mentioned below, the direct drive A4 propeller is too small to be useful in a chop. For the above reasons I changed out the A4 to a used diesel and fitted a 16" KiwiProp . In part due to long motoring sessions sometimes required when cruising our coast and needing to transit 75 miles and get back to work on time. (I know, that in itself is overated :) My fuel consumption went from 4 litres per hour to less than 2 litres per hour @ 5+ knots and I don't drop to 3.5 knots in the chop. Cheers, Russ Sweet 35 mk-1
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