Input shaft seals, why different sizes?

I have a '87 GT200 E200STLCUA lower unit, and I'm replacing the input shaft seals below the water pump. Every where I look these up it tells me to use 329923 and 339922 seals. My shaft size is .875 and the 339923 is for a .875 shaft but the 339922 says it's for a .822 shaft size. Is is correct for me to use this .822 seal on a .875 shaft? I don't feel a step on my shaft and I checked it with calipers and it measures .875. I sure could use some help here. http://www.bassboatcentral.com/smileys/praying.gif

Call Eddie Pope,423-336-5618 He is the guru on the J/E gearcases!!

Can't speak to the dia of the seals but if it calls for two different P/N's one is usually installed with the lip facing down toward the case and the second one is installed with the lip facing up away from the case. One keeps pressure in the other keeps water out. Some applications will call for the replacement of two seals as described above with one double lip seal.
A dealer can check it out for your specific application.

You're O.K. here, the 922 will be on top, the 923 in first. Be sure to use some sort of sealant around the outer perimeter of each, and inside the bore before installing. The little circular springs will be on the fluid side when installing. http://xs-s.com/zf/images/smile/emthup.gif

My only question was about putting a .822 dia. seal on a .875 shaft, I went ahead and installed it and everything looks fine. I checked with my dealer and looked this up on several sites, and everything said this was correct. I just felt it was odd and wanted to make sure about it.
Thanks for all your help.

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Who says that the seal is for a .822 shaft? You do mean part number 329922 and not 339922, right?

This is what it calls for and this is the sizes:

Sierra OEM Shaft OD Width
18-2061 329922 0.822 1.375 0.195
18-2062 329923 0.875 1.375 0.207

You are quoting 3rd party info, not factory info which we believe in here in this forum.