Gear Ratios for ZF 15 MIV Gearbox

My ZF15MIV Gearboxes have gear reduction ratios as follows -

'A' Pos 'B' Pos
2.134 2.224
2.718 2.224
2.995 2.224

I have searched the web a fair bit regarding the 'A' Pos ratios. I can find no detail as to how these different ratios are set up/selected.
I ask this question because a number of propeller suppliers have asked which one I would use. Could someone please explain what I am missing in my understanding?

 

are they asking for the ratio?
that is all they would need to know about the gearbox itself?
One thing I have noticed abt suppilers of ZF(Not the zf site itself) is that they all have differnt measurements, some are right some are wrong , which makes it difficult when you are loading a pdf file into your drawings to arrive at the right point for the gearbox , shaft intersection

 

Zf gearboxes turn either way without a prob and are designed to do that. The prob is that as you can see from the chart the ratios vary slightly.

The prop man wants to know if you are using A for Port or Stb

If he knows this he can alter the pitch a little on one prop to compensate for this so that your engines will be synchronized.

Thats a good prop man!!, most don't bother resulting in an irritating
whooming noise from the unsynchronized engines along with different load and fuel consumption.

 

Thanks for your replies, very much appreciated.
What I have been asked is "Which 'A' Pos I would be using, 2.134 or 2.178 or 2.995?"
I cannot find, from ZF or Nanni, which of these ratios is "set" or how that may be done.

 

It would appear that I have misunderstood the question then.

So it looks like the Z15 is available in those ratios.

If you have the boxes the ratio will be on a label on the box.

 

The ratio is set in the factory, you can't move between options at the flick of a lever. So you need to work out which ratio you're already on. It should be marked on the gearbox, otherwise if the gearbox is currently off the boat. turn one end and see what happens at the other.

 

[ Turn one end and see what happens] Not if its Hydraulic!!!!!

 

Thank you Gentlemen,

Frosty, I found it on the boxs in the fine French print, now I just have to gather the drive line
items.