I-R Gear Housing?

[astronutski]

I see a chapter in the Mercruiser Alpha One manual called "I-R Gear Housing" but I can't figure out what it is, it looks the same as the other chapter to me.
Does anyone know what this I-R Gear Housing is?
http://www.boatfix.com/merc/Servmanl/6/6C3R3.PDF

Thanks.

 

[Bt Doctur]

thee is the MC1, the R, the MR and the Alpha1 basically all the same internally ,The R and MR are modifications of the drive and housing.
The MC1 has a rounded cav plate and lifting eye the R, MR has a square plate and flat top plate