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225 most efficient RPM

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x32

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I have a Grady Whitesailfish with daul 225 and wonder if anyone knows what is the most efficient RPM to run at?
 
Every boat/motor set up is different, so there is not a pat answer to your question.

You can make you own efficiency charts in Excel if you have the Honda digital gauges (or similar) where you can get an accurate reading of fuel consumption in real time. Here is the way I did mine.

First, in calm water get up to cruising speed and find your best trim position and leave it there. You also want to make sure you are doing this with your "typical" weight in the boat - say around 1/2 tank of fuel, normal passenger load, and normal equipment on board.

Then set up a worksheet with three columns - RPM, MPH (using your GPS), and GPH (gallons per hour)

Take at least 25 observations (the more the better) at various rpms through your whole range - 1000 to 6000 rpm's.

Transfer your numbers from the worksheet to Excel and sort them from lowest to highest RPM

Then use the Excel line chart function to make two charts - RPM (y axis) vs. GPH (x axis), and RPM (y axis) vs. MPH (x axis).

Note that the rpm's should highly correlate to you GPS MPH.

If your engines act like mine, you will see two rather flat spots on those charts - one around 2000 rpm and the other somewhere between 4000 and 5000 rpm.

Your most efficient cruising speed will be at the rpm's where the second flat spot starts. That is, where you are getting the highest rpm's (or MPH) at the lowest fuel consumption.

On my 225, the sweet spot is 4400 rpm's where I am burning 8.3 gallons per hour. That translates to 29.5 MPH.

Hope this helps.
 
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