As is likely evident to all, Larry's posted figure for diesel fuel consumption of about .06gal/hr for each HP is the recriprocal figure posted by someone else, quoting about 18 HP per gallon consumed. (although actually 1/(.06) is about 16.6 rather than 18). I may not have seen all the posts, but these typical fuel consumption figures assume the engine is turning its correct maximum rated RPM at WOT. If the prop is too big for example, the engine throttle will be more fully advanced than normal at a given RPM and fuel consumption almost certainly higher. Two cycle Detroits are likely a bit less efficient than these average consumption figures, new four cycle electronic control engines likely more efficient. If you have the spec curves for your engines, the "fuel-propeller load" curve should give your approximate fuel consumption. For my 8V71TI Detroits, at 1600 RPM, for example, spec curves shows consumption at about 8.8 gal/hr, shaft HP about 150, equating to about (8.8/150) 0.6 gal/hp/hr. My best estimate from actual experience suggests this is a bit optimistic. I think I use closer to 10 gal/hr which equates to about 0.67 gal/hp/hr. (based on refilling fuel tanks against hours of use.) Rob Brueckner Hatteras YF