I took this lower unit off seven years ago so reassembling it has been interesting to say the least. It's about ready to go back on, and all parts are accounted for, except I have one O ring that I'm not sure about. (It's about 1/2" ID)<br /><br />There is a groove just below the spline at the top of the drive shaft. It looks to me as if that O ring belongs there as I can find no other logical place for it. Am I right? The only other O ring I've had in this project is a large one that belongs on the water pump .. it came with the kit. This one was in my box of parts.<br /><br />I have a manual but I've not been able to find it. I also have the CD version of a manual, but its not been much help.<br />Thanks in advance<br />Tom --- 1958 Super Seahorse 35hp RDSL-20