Show your mathmboatworks wrote:I need to test the tachometer to see how accuarate it is, but I am guess at 1700rpm, and 7-kts, is its sweet spot. The fuel burn is about 0.7-gallons/hour at that speed. By some rough calculations, it is only using about 40HP at that speed.
An A-27 hull should be able to be pushed to 7 knots on less than half of your estimated 40 HP
A well tuned diesel engine uses about .4 pounds of fuel per hour for each horsepower it produces, so your .7 GPH would be about 5 pounds of fuel, dividing this by .4 we would get about 12.5 HP
I know my last sailboat, a 15,000 lb 34 footer with a 25 hp diesel would cruise to hull speed using just 9 HP with 1/2 gallon burned per hour
Don