Can anyone explain pinion height?

[25two.stroke]

Why does mercury do this.
3.0L pinion heights are WAY higher than 2.5L for the SAME GEARS. I know they are not the same part numbers, but they are the same gears. They are just trimmed a little differently before they are hardened.
Why does 3.0 use flat 4 (which is like 0.030" higher) instead of flat 7 like a 2.5 for 1.75 and 1.62
Yet 3.0L 1.87 still uses flat 7
And in my experience 1.75 and 1.62 gears in a 2.5 never wanna shim correctly at 0.025" off of flat 7
Does anyone use flat 4 for setting the pinion height on 2.5 1.75/1.62 sets?

2.5L:

3.0L:

[billybob]

Always use the rear disc. with cutout, when checking pinion gear height. To make sure tool is centered in prop. shaft bore. Because pinion gear height, is always set at .025 on tool.
And forward gear can be shimmed in or out to get correct backlash.

[25two.stroke]

Always use the rear disc. with cutout, when checking pinion gear height. To make sure tool is centered in prop. shaft bore. Because pinion gear height, is always set at .025 on tool.
And forward gear can be shimmed in or out to get correct backlash.

Tell me somethin I didn't know LOL.

Thank you for confirming that...but thats not really what I was asking. Maybe I wasn't clear. I'm tryna figure out what people set 1.75 and 1.62 gears at in a 2.5. Do they set the pinion at 0.025 off of flat 7 or flat 4? And why would the pinion height be different for a 2.5L vs a 3.0L with the exact same gears and driveshaft.

[25two.stroke]

As I measure flat 4 is 0.038" taller than flat 7. So which disk you use makes a BIG difference. I just don't understand why 1.75 or 1.62 gears when you put them in a 2.5 they want the pinion height set 0.038" lower than in a 3.0.

Has anyone ever set the 2.5 ones off of flat 4? If so then is the fwd gear backlash easier to set than if you measure off of flat 7 and then set backlash. If I use flat 7 I have a hard time getting the pinion height low enough. Then with the pinion height 0.025" off flat 7 the fwd gear backlash ends up being WAY too tight even with no shims. This makes me think that the pinion height should actually be set off flat 4 for 1.75 and 1.62 regardless of what powerhead is above it...

[billybob]

OK, so you are talking about putting 3.0 litre gears, in a small V-6 gearcase, to achieve a higher gear ratio. I guess.

[25two.stroke]

OK, so you are talking about putting 3.0 litre gears, in a small V-6 gearcase, to achieve a higher gear ratio. I guess.

Well, kinda. Mercury made 175 and 162 gears for 2.5s. Most often they were sold as "kits" to change to a higher gear ratio. The 200xs and some 150/200 ProMax motors came from the factory as 1.75. The only difference I see in the 2.5 175 gears vs. the 3.0 175 gears is the clutch engagement area. 3.0L gears don't ratchet so the clutch engagement area is square. On 2.5 gears the clutch engagement area is machined into ramps for ratcheting. Same tooth dimension on the gears though. So I don't get why mercury would have the gears shimmed totally different between the 2 cases. The driveshafts are the same (double bearing) and theoretically the case itself makes no difference in how the gears should engage each other.

To make things more complicated, when you put 1.87 gears in a 3.0L (yes Mercury did make gear conversion kits for 3.0L to make them 1.87 and some even came from the factory that way) the book says you shim them the same as a 2.5 1.87 set 0.025 off of flat 7 and 0.025 backlash. This re-affirms my believe that the case they are in (2.5 vs. 3.0) makes no difference. The pinion height is dependent on how the gear is cut. So is the 2.5 book wrong about what flat you use for the steeper gear?

[LakeFever]

Are you certain the gears are the same? Two cut and five cut gears have considerably different set up numbers

https://m.youtube.com/watch?v=6lGIvOXVfcY

[25two.stroke]

When I measure the gears the 2.5 and the 3.0 are the same tooth size for each ratio. The teeth are different heights on the inside vs. the outside.

[LakeFever]

I have zero knowledge of merc gears. In the car world you have to pay attention to how the gears were cut. Two cuts set up a lot tighter than five cut. You can usually see by the look of the teeth on the ring gear from the outside edge. Five cut look like ramped triangles where the coast side is quite a bit steeper than the drive side. Two cut are pretty similar in angle drive/coast respectively. Ive had gear suppliers send both types in the same box, same part numbers. The vid above is also helpful’ish

[patchesII]

You don’t see 1.62 2.5 gears very often. I’d say a lot of people didn’t know they exist