fuel effiency?

[vidar]

i got a 20 feet daycruiser with a 85mod 140 suzy total weigth of 3300 pounds. when i cruise at 20 knots i use 6.6 gallon a hour.3800rpm prop13x19.max rpm only4400. also have a 13.75x15v/cup that turn 5500 but have to use 4400 for 20 knots and the engine makes a mutch more noice....no prob getting on plane w 13x19 and no exessive heat..but coud the other prop get better milage?? please give me some hints ..thanks.

 

[JB]

Re: fuel effiency?

I think you would be better off all around with the 13.75X15" prop, MA.<br /><br />You might improve your fuel efficiency some, but it will definitely improve your engine life to use a prop that allows it to reach optimum operating rpm. <br /><br />I think you will find that you reach 20mph/4400rpm with the same or less throttle than you now use to reach 20mph/3800rpm. That is a sign of better efficiency.<br /><br />Good luck.

 

[roscoe]

Re: fuel effiency?

If your engine turns lower rpm to achieve the same speed, it will get better mileage. But, the long term effects of lugging your engine could be costly.