O-ring question on 1965 9HP VWB19077A Sea King

Had my Sea King lower unit laying on it's side while removing the cup that houses the impeller. While jostling the unit, a very thin broken o-ring feel on the floor. Don't know if it came from on top of the impeller case or underneath the stainless plate under the impeller. OR did it come from one of my other projects and just fall off the bench? Even though it looks to be about the diameter of the drive shaft a good look didn't help me find a place this skinny little o-ring may have been or would do any good. Anyone familiar with the VWB series know the answer or maybe have an exploded parts view they may share by PM? Thanks!

That is a chrysler built motor 1965 9.2hp I couldnt find any diagrams below 1974 is there a groove in the driveshaft just below the upper splines?

Yes, about 1.5" below the top of the splines there is a groove around the shaft. The splines continue for about another .25" below the groove.

It probably keeps water out of the splines in the crank. Lightly grease the splines and put a new o-ring on when you install the lower unit.

Thanks very much. I'll bet I can find an o-ring that size somewhere. I never thought to look that far up the shaft! Tunnel vision at it's best.