Prop Pitch Measurement

February Tech Notes

A Supplement to The Engine Analysis Software


The Prop Duplicator

I have been using the Hughey Propeller Measuring Gauge for 25 years and have never thought much about it. Withing the past 10 years I have been getting interested in the some of the finer points of model boat propeller design and modification. I decided that it was time to splurge and buy one of the Woods Pitch Gauge Measurement Devices. What a terrific tool and a precision piece. I can analyze the pitch and the efficiency of propellers VERY WELL with this gauge. I have developed a system and spreadsheet, which I will describe. I made up a comprehensive spreadsheet in Excel to keep the measurement and comparison records, and additionally to do some of the mathematical calculations. I will describe how I measure a prop with this gauge and if you find it informative and a necessary tool, GREAT! First, you can get the Wood's Pitch Gauge by visiting

If you are interested in prop measurement and documentation, you should download the FREE spreadsheet before you analyze this tech article. Click Here to Download. There is also an image that shows where you should mmeasure on the Gauge to set the 70%.

Here We Go!

You will want to describe the prop, the date, and your estimated engine RPM. Take calipers and measure the total diameter of the prop and input this in decimal measurement in the column "Measured Prop Diameter Inches". This will output the conversion into Millimeters. The next column (Column X) is the MOST IMPORTANT setup measurement outputted. This represents the distance you will want to set with your calipers BETWEEN THE TWO POINTS SHOWN ON THE DRAWING IN THE ZIP PACKAGE OF THE MEASURING GAUGE. This figure adjusts for the centerline of each of the posts and calculates 70% outward from the center of the propeller shaft hole. Why do I move out 70%? I believe that this is the area on the propeller that does MOST of the work. ALL my measurements are taken at this 70% point. You will want to use the first 3 steps of the pitch gauge. The first step is the base point and you use that to set ZERO. Once you ZERO the Gauge, you will want to move to the second step and input the degrees you read into the .0625" column. This will output the pitch. Next do the same for the 3rd and 4th step and input these degrees into the .125" and .1875" columns. The prop is placed on the shaft upside down and the sharp pointer is positioned using the calipers BETWEEN the large shaft and the small shaft as outputted in the .70 from hub Measurement. Then adjust the prop so the small pointer just hits the Far Trailing Edge of the prop (it almost drops off the back). Set the pointer at 0 degrees. You will need to input the MPH that the prop actually runs on your boat and the amount of slippage is automatically outputted in the column Percent Prop % Slippage. This is helpful to find the best and most efficient prop for your application. There are a few props shown as information. After you get used to the Woods Propeller Measuring Gauge, I know it will become one of your most valuable tools! Let me know if you have any interesting props which don't seem to fit any mold, and we can try to figure out why it is better than anything else. Until Next Month……….

ENGINE Analysis Software for the Serious RC Competitor



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