In a message dated 5/16/2005 10:06:53 P.M. Eastern Daylight Time, malcolm@tennantdesign.co.nz writes: Shame you could not use the Yanmar fuel consumption charts. Our experience is that those manufacturers fuel charts are usually within about 2% unless there is something very strange going on. I hope this sheds a little light on the issue. Thanks for your insights, Malcolm. I'm sure the Yanmar curves are accurate, but the only ones I could find for the 75-hp engines (at: _http://www.yanmar.com/marine/pdfs2/JH.pdf_ (http://www.yanmar.com/marine/pdfs2/JH.pdf) ) show values only for engine speeds of 2000 rpm and above -- nothing for the lower speeds. (At 2000 rpm, they show a (maximum) consumption of just under 1 gal/hr.) If I understand you correctly, Malcolm, you're saying that no economy benefit is to be had by single engine operation -- at least in the case of simple fixed-pitch (3 or 4 bladed) props which are allowed to freewheel -- with the dead engine in neutral gear? Correct? If this is true, I'd venture to guess that it's because the drag of the freewheeling propeller (including gearbox drag) overcomes the potential advantage of single-engine operation. I know diesel engines can be pretty efficient at low speeds (unlike gasoline engines), so I'm willing to believe that this could well be true. I'd certainly be interested in seeing some documentation on this subject if anyone knows a good source. Henry

>Henry Clews wrote: >I'd certainly be interested in seeing some documentation on this >subject if anyone knows a good source. Sounds like a good project for an engineer like you, Henry, after you have broken in your PDQ 34 Powercat next year. Maybe there will be a a new magazine then to publish such a report. --Georgs -- Georgs Kolesnikovs Power Catamaran World http://www.powercatamaranworld.com