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Old 02-02-2021, 13:44   #1
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Prop sizing - what does it represent

I have a MD2040D Volvo engine. I might have to replace the prop. I am seeing numbers in the schematic like - 14 x 10 x 25.

I believe that:
The 14 is a measurement from the tip of the fin to the tip of the other fin. Two fins on my prop.
The 10 is the pitch
What is the 25?

Am I correct on the definition of the other two numbers?

Thanks
Aloisius
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Old 02-02-2021, 13:45   #2
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Re: Prop sizing - what does it represent

25 mm is your shaft diameter and yes the the other numbers are correct
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Old 02-02-2021, 13:48   #3
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Re: Prop sizing - what does it represent

That's also a left hand prop. It would also be good to know if the taper on the shaft is 10 to1 (most likely) or 16 to 1.
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Old 02-02-2021, 13:48   #4
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Re: Prop sizing - what does it represent

If you do not know the pitch on a prop, the marking is not clear, is there a way to measure the pitch on an existing prop?
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Old 02-02-2021, 13:50   #5
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Re: Prop sizing - what does it represent

Yes bring it to a prop shop
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Old 02-02-2021, 13:55   #6
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Re: Prop sizing - what does it represent

if you have a protractor you measure the angle the blade makes from perpendicular at 75% of the radius. So if your prop is 14", then .75*7=5.25" from the center of the prop hub. There are tables to convert degrees of pitch to inches of pitch.
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Old 02-02-2021, 13:59   #7
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Re: Prop sizing - what does it represent

But I wouldn't buy a prop based on schematics unless your absolutely sure that the prop was an unmodified original and you verified that the prop could allow the engine to get to 90-95% of rated RPM.
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Old 02-02-2021, 14:01   #8
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Re: Prop sizing - what does it represent

I will pull the prop this weekend and see if I can read the markings. Thanks!
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Old 03-02-2021, 14:33   #9
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Re: Prop sizing - what does it represent

You can go to 5 prop shops and get 5 very different answers as I did years ago. There are 2 sources that I have faith in: 1) Propeller Handbook by Dave Gerr and 2)http://www.vicprop.com/displacement_...tion=calculate
The vicprop online calculator will be the fastest way.
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Old 03-02-2021, 21:10   #10
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Re: Prop sizing - what does it represent

If the pitch has been altered by a shop , the new pitch is usually stamped on the end of the hub at the small end of taper.
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Old 04-02-2021, 00:46   #11
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Re: Prop sizing - what does it represent

When I had to replace our propeller, I looked into the engine specification related to the size and yacht brand.
Good lack
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