Gear ratio determination
 

Might be over thinking this but the ratio doesn't add up so I'm missing something.

Original Drive B3 2:0 ratio so it should have 32/27 uppers and 16/27 lowers. I know the lower has 16/27 gears because I rebuilt the lower section a few years ago

After the repower, I bought a complete brand new B3XR 1:81 ratio drive. Boat would barely come up on plane with 22 pitch props. So I dropped the lower, and installed my original 16/27 lower. Boat comes right up and all is sort of good, for the most part. Doing some research I'm only seeing the XR upper with gears of 16/19. Using the 16/19 upper and 16/27 lower it comes to 1:42 ratio. This just doesn't add up so there must be other gears used in the upper. When I manually rotate the drive, there is 2 upper rotations to 1 lower, so it is a 2:0 drive, and must have something like 32/27 gears in the upper.

Anyone know of Merc listing other gears for the upper?

Edit: Mistyped title - determination

The XR (16/19) and the 27/32 helical gear set net the same ratio, the 27/32 is used in the 1.5 B1, 2:1 B2,B3

There is only one flavor of XR upper gears, to get a 1.81:1 B3XR, they use a 17/26 lower gear set.

When you put the 16/27 lower on it, you went back to 2:1 just like the original drive

Isn't that transposing the numbers?
But maybe the site is transposing the numbers

16/19 = 0.842
19/16 = 1.187
32/27 = 1.185
16/27 = 0.592

Final calculation, 1.187/0.592 = 2.00506
That would answer my question, its the web site which is not listing it correctly, and they get their info from Merc.

http://www.mercruiserparts.com/bam/s...0991/11406/130

Thanks, I knew it was simple, just over looking the obvious
[ATTACH=CONFIG]565996[/ATTACH]

They're transposing the 32/27. The 27/32 helical used in a B1 and a 16/19 XR both use a 15/19 tooth count lower gear set to net a 1.5:1 reduction

The math doesn't work out with 27/32 or 16/19

27 divided by 32 = 0.843
16 divided by 19 = 0.842

Use either of these numbers and divided by (15/19 =) 0.789 comes to 1.068 (0.843/0.789 )

It has to be the other way 32/27 or 19/16

The pinion in both upper and lower is the smaller #. You have 1.185 reduction for the helical and 1 .187 for the XR multiply either of those by 1.266 ( the 15/19) and that gives you 1.5 ( and some change ) total

The only way to get 1.266 is to divided 15 into 19, not 19 into 15. A mathematic equation makes the first number is divided by the second
Exp: 6 ÷ 3 or 6 ⁄ 3 means the division of 6 by 3 = 2

https://en.wikipedia.org/wiki/List_o...atical_symbols

I apologize for the confusion, I was just using the slashes to separate the 2 numbers