Agree with BoatBuoy.<br /><br />Maybe it's a good rule of thumb, and maybe it'll work for many boats, but it's not a racing certainty.<br /><br />Let's face it - most of us throttle up, down and sideways anyway, unless we're doing a very long run on even water.
I looked up the rpms per mph and the mpg specs for two boats, one a 19 foot outboard and one a 26 ft FourWinns Vista Cruiser 5.7 outdrive. <br /><br />The outboard got low mileage and high rpm/mph at 3000 and 3500 rpms. It got higher, consistant mileage and lower rpms/mph once it got to 4000 and above. The outdrive cruiser got the best rpm/mph at 4800 (wide open) but got poor mileage there. The best mileage was at 3000 rpm where the rpm/mph were higher than at the higher rpms. Using the chart, you would run the cruiser wide open to get the best miles per gallon but you'd wipe something with the chart after you filled her up at the gas pump. <br /><br />Looks like you can run outboards efficiently at higher rpms but the big sterndrive V8's suck gas big time when the revs go up.
