Mercury Prop Measuring Tool

thingiverse

I designed this tool for measuring Mercury propellers. You insert it into the hub on the opposite side of where the splines terminate (the smooth bore side). This gives you a true center that sits proud of the hub so you can get a radius measurement on one of the blades. Use a vertical surface and butt the prop up against it. Rotate the prop to make sure you are measuring the O.D. properly. If you don't rotate the prop you may accidentally have the vertical surface tangent to a smaller portion of the blade. This method is still not super precise, so just use your best judgement. Captain Obvious Hint: If your ruler/scale doesn't start at the edge make sure to add that extra length. Mine is 0.165" from the edge, for example. Would be nice to engineer a vertical surface that is exactly as tall as it needs to be so that dial calipers or a properly positioned ruler/scale could be used. I know I called the bigger version "Large Hub", but that is a bit of a misnomer. The normal size will measure most "Small Hub" [4.25" gearcase] and "Large Hub" [4.75" gearcase] propellers, but I found that my Quicksilver HighFive 5-blade props had a larger I.D. on the smooth bore side of the hub. Thus the "Large Hub" version. The regular version has a loose clearance fit and the "Large Hub" version has a slight interference/transition/friction fit. This is mostly by accident because I am an amateur. I have included the Fusion 360 files so you can modify them 0.1 mm or so if they don't fit after you print them out on your particular setup. After measuring 8 propellers I noticed none of them are exactly as listed in the catalogs or Google searches. You might need to round up or down to the nearest quarter inch to determine what it was sold as. This might be due to casting flaws, material removal when grinding, etc. See Post-Printing steps for finishing the nib