Paul Kruse had written concerning the fuel consumption of a 25 hp two stroke outboard at full speed and full load: >>Used to be about three gph, or a little more; but they are doing much better >>than that these days. At 03:01 PM 3/25/99 +1200, Steve Darden commented on that, with data supplied to him from his NZ Yamaha dealer: > max fuel consumption, under load, wide open throttle, 5500rpm = 12 >liters/hour I would have guessed that current models are better than that. Perhaps some of the very fuel efficient models from the USA are not available in NZ, or perhaps the more fuel efficient models are only available in the larger engine sizes. (JTOL) [snip dealer estimates for other throttle settings.] >The 15HP is > 7.3l/h max usage That looks pretty linear to me, without running the numbers to see how linear it is. >They said designer Nic De Waal is probably correct that the 25 will be >more fuel efficient than the 15 in planing operation (lower RPM). I would agree, just guessing according to what at typical specific fuel consumption curve looks like. The difference would be very small, though. >Your figure of 3 USgal/hr would seem to match their quoted 12L/hr full >throttle. Do their numbers look correct to you? Everything else is completely bogus marketing hype. You have no way at all to know how much you will burn at lower throttle settings, unless you can determine how much power your boat will require from the engine at those settings. If it requires half the power at a particular setting, for example; then it will burn close to half the fuel. It is also possible to burn less than the full three gallons per hour at top rpm, if you are pulling less than full power out of the engine. That is what will happen if you undersize the prop, or under load the boat for a particular trip. +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ :: Paul and Cindy Kruse :: KJV Joh 14:27 Peace I leave with you, 165 South Kenneth Court :: my peace I give unto you: Merritt Island, FL 32952 :: not as the world giveth, give I unto you. E-mail: plkruse@iu.net :: Let not your heart be troubled, 407-453-6206 :: neither let it be afraid. :: +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++