Just curious

[GatorMike]

Not that important because I seldom push my luck but I figured if I ever got into the situation it would be a good thing to know. If one were crusing on an empty tank what would be the ideal throttle setting for maximum mileage? Idle speed, just on plane, 75%, certainly not full throttle?

 

[Paul Moir]

Re: Just curious

Typically it's just a little beyond just-on-plane, check this out:<br /> http://www.johnson.com/media/PE224.pdf <br />But it depends on what type of boat you have. Most normal planing power boats are abysmally poor on milage at lower speeds though.

 

[bayman]

Re: Just curious

For those who go through a lot of fuel, Floscan makes some good devices which monitor your fuel usage so that you can tell what your ideal and most fuel efficient speed would be.<br /><br /> http://www.iboats.com/mall/index.cgi?keywords=floscan

 

[GatorMike]

Re: Just curious

Thanks....I guess I would have been dead wrong. My second guess would have been right on. Logicaly I figured idle speed would be best then just above plane.

 

[QC]

Re: Just curious

Some boats do get their best economy at idle. Kinda depends if the idle speed is at or about the natural hull speed of the boat. Other than that, just after she starts to plane as Paul mentioned. I have noticed that most I/O tests show the best economy (other than the low idle champs) between 2500 and 3500 RPM. The overall faster boats do better toward the bottom of that range and slower ones toward the top.<br /><br />BTW, if you had a throttled engine (gasoline) that put out exactly the correct amount of horsepower just to plane efficiently and no more, then wide open throttle would be the best fuel economy. I know it sounds messed up, but it's basically true. That same engine may not have enough power to get her to plane though, so pretty stupid point. Odd thing is that throttled engines are most efficient when operated at WOT, particularly at lower RPM than we run them. Auto manufacturers have worked for years to get the throttle further open in more conditions. That's why they running them slower and slower and try things like Continuously Variable Transmissions (CVT). This is part of the Hybrid story too. They run the gasoline engine like you would a generator . . at WOT.

 

[umblecumbuz]

Re: Just curious

Price of fuel - I guess we'll all be trying to cruise on empty tanks soon.

 

[Silvertip]

Re: Just curious

There are two ways to measure economy. Gallons per hour (GPH) and Miles per gallon (MPG). The two don't necessarily happen at the same engine RPM. Go to Yamaha's web site and look at the Performance Bulletins listed for their engines as used on various boat types. The graphs illustrated will give you an idea of where you should run your engine to achieve best economy.