Can you help me understand these prop markings?

[OrangeCrush]

Hello,

I’m getting a new Maxprop and I want to identify my current bronze 3-blade fixed prop so that I can accurately report the pitch to Maxprop and so that I can try to sell it.

On the side of the hub it appears to say D 16 P 11, but right under the 11 is a 9. The diameter is indeed 16”. Would that be a pitch of 11” (or 11.9”) or something else?

I can see a number on the hub which appears to read either 1451074, H51074 or maybe just 51074. The first character is a bit scraped up. It also shows the letter P in sort of a block letter style, like a logo. It made me think of Perko but I can’t find that exact logo or any of these numbers associated with them. There are also some assorted letters partially stamped around, like “R” and “BA” and “HYD” and “OLUM” (if I’m reading them right).

I would also appreciate any tips on what the old prop might be worth and how to go about selling it. It has no dings on the blades and it was professionally balanced last year. It’ll polish up very nicely.

Thanks!

[tkeithlu]

Probably you have a 16" diameter 11" pitch propeller than someone repitched to 9". Repitching is a surprisingly crude process. You lock up the prop on its shaft, clamp a 2x4 to the blade, and bend away.

[fstbttms]

Originally Posted by tkeithlu

Probably you have a 16" diameter 11" pitch propeller than someone repitched to 9".

This ^^^

[tkeithlu]

As freely plagiarized from the internet, here is how to measure it yourself:

To measure the pitch, lay the propeller flat on a table, measure 75% of the way from the hub to the tip, and draw a line across the propeller blade. Measure the width of the blade at this point, along the surface of the table (i.e. the width of the blade's shadow if there were a light on the ceiling overhead).

The pitch is then given by the formula:

pitch = 2.36 diameter height/width

There’s nothing magical about the number 2.36; it’s just 75% of π (pi), because we’re measuring pitch at the 75% diameter mark.

The reason we measure pitch at 75% of the diameter is two-fold. Generally, the pitch of a propeller is not completely constant, varying somewhat from hub to tip to optimize it for the different linear speeds at each point along the blade. The pitch at 75% corresponds roughly to the average effective pitch of the propeller. Secondly, the propeller is sufficiently wide at 75% to allow one to get reasonably accurate measurements of blade width and height.

[OrangeCrush]

Thanks! I finally found the receipts from the shop that did the balancing and they listed the propeller at “RH 16x9” so I’m guessing you’re right about the re-pitching and 9 stamp. I will measure it myself to confirm.

[tkeithlu]

Want to learn something else wierd today? Did you know that your having a right hand (RH) prop means that you have a left hand engine? Yep. Learned that the hard way.

Bought my engine military surplus. "It's a left hand," they said. "Oh, I need a right hand. Please change the camshaft to right hand," said I. Five years later I fired it up. Prop turned the wrong way. "What the !@#$," said I. Turns out people doing props stand behind the boat, and if the shaft turns clockwise, it takes a right hand prop. Mechanics, though, going back to hand cranking motors from the FRONT end of the motor, say, "It turns clockwise, it's a right hand ENGINE."

I have a left hand prop and a boat that docks kinda funny.

[OrangeCrush]

Haha good to know, thanks. And a billon in Spanish is a trillion in English!

[Lancerbye]

I have two right hand engines, one RH and one LH props. The rotation of the prop is determined by the transmission with the gear reduction, not the engine rotation.

[Godshalk]

I am in somewhat similar circumstances and found this person at the mfr of MaxProp to be very helpful:
PYI Inc.
Fred Hutchison
12532 Beverly Park Rd.
Lynnwood, WA 98087-1524 USA
e-mail: hutch@pyiinc.com
web site: http://www.pyiinc.com
Office Tel: 425-355-3669
800-523-7558
Skype: fjhutch
Fax: 425-355-3661