ISO Propshaft question

[Noahsdad]

Hi all,
We have just been lifted out and it is apparent that the propellor is almost past its expiry date.
I've been offered a very good price on a replacement 2 bladed folder for a 25mm ISO shaft.
I got the old prop off today and measured the shaft diameter at both ends of the taper and got 25mm and 20mm respectively with a 50mm taper. This I can see is a 1:10 taper. Great.
What confuses me is that on searching the Internet some 25mm ISO shafts are 25mm and 19mm with a 60mm taper and is also 1:10 and another seems to have an ISO shaft that has a 55mm taper that is also 1:10.
I understand the maths though confused as to whether the prop will fit!
Now I'm sat at home (old prop in Gosport) I'm thinking I should have measured the internal length of the hub of the old prop.
Am I missing something?
Thanking you all in advance.

 

[Len Ingalls]

http://www.propellerpages.com/?c=tech_info&f=tapers

I believe all 3 that you quoted are the same 1:10 taper.If you measure the diameter at 50mm from start of taper,you should get 20mm dia. at that point?
The fact that one mfgr carried on a little further beyond 50mm shouldn't make any difference to the rate of taper(1mm taper in 10mm length).
The front face of prop hub will fetch up at same spot,I believe. Cheers/Len

 

[macd]

As Len said, the prop shoud fit the taper, and the front face of the prop should be in the right place*. But surely the issues with a longer taper are whether the keyway will be right? And can the securing nut be brought up against the prop boss?

* unless the prop is left 'hanging' on the woodruff key.

 

[Noahsdad]

Thanks for the replies. I understand all of that.
What I really want to know is my shaft ISO?
Thanks again.

 

[macd]

It's 25mm and 10:1 whichever way you measure it, so yes. But who's to know whether the maker didn't get creative with his conventions? Perhaps all you can do is offer up the prop and take it from there.

 

[Noahsdad]

Cheers all, ordered prop today and hoping for a seamless fitting!