I have just replaced seals etc. in lower unit and will attach to motor tomorrow. Earlier this spring I replaced the water pump impellar and never noticed an o-ring on top of the drive shaft. Upon removal of drive shaft this time I still have not seen an o-ring on top of the drive shaft. The Seloc repair manual actually shows a picture of the o-ring just sitting on top of the splines. My questions are: did the o-ring stay on engine, does the o-ring go on ring groove below splines and when installing drive shaft do you just put some grease on top of shaft and stick o-ring to it and hope for the best? I have looked up inside the shaft and do not see any sign of ring. I have one o-ring left from repair that is 1/4 inch i.d., does this sound about right size? My engine is rude, fastwin 18, type D shift with plate on stbd. side. Thanks for any help. John