borg-warner gear ratio

[tomJ]

I have a borg-warner 71cr hydraulic box on my perkins 4236,and am trying to get the gear ratios as I wish to fit a feathering prop.The only markings I can find are on the rightside,as you look at the rear of the box,and all but hidden under the rear engine mount.they seem to say LH(logically left hand)71 76(or perhaps 7G)
I have spun the motor,using the starter, and counted the shaft revolutions,but am not sure this works on an hydraulic box.
the results I get are
9 turns of the crankshaft 5 of the shaft so 1.8
11 6.25 1.76
10.5 5.5 1.9
13 7.25 1.79
not really absolutely conclusive.
is there another way of telling?a number stamped where I have yet to find it?or does the 76,7G mean something to somebody?
I would love to say the prop company have been very helpful.....
many thanks in advance
Tom

 

[tr7v8]

Just done a search on google this link shows your engines with 1.5:1

<A target="_blank" HREF=http://www.conwaycommercial.com/490.htm>http://www.conwaycommercial.com/490.htm</A>

But another says Borg Warner Velvet drive gearbox AS3-71CR, ratio 2.1:1. ...


Jim
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[Bejasus]

A check here shows BW 71 as having 1.52:1. However a check with Lancing Marine should answer your question.

http://www.arweb.co.uk/argallery/h00

 

[pvb]

Velvet drives...

Borg Warner Velvet Drive gearboxes usually have 2 distinct parts. First, there's the actual forward/reverse gearbox. which is direct drive (ie 1:1) in forward (and perhaps a little different in reverse, say 1.1:1). Second, there's usually a planetary reduction gearbox bolted on the back - these are often 2.1:1 ratio. The "CR" suffix means the output shaft rotates anticlockwise when viewed from the back.