? for Johnson/Evinrude 9.9/15 Lower Unit Experts

[CER79]

Picked up a used lower unit for my 1991 15 hp because the drive shaft broke in the lower unit just above the gear. Thought about changing the shaft out only but got a good deal on the lower unit including the prop ($150). From what I have read the lower units are suppose to be pretty much the same for 1974 to 2007 for the 9.9 and 15. Got the replacement lower unit home and noticed the drive shaft has a groove in it at the top near the splines that engage the power head that my original doesn't have. After a little research I found out that it was made to take an O ring on some of the older models and that on the newer models the oring is in a recess up in the power head. My question's are what is this O ring used for? Can I safely use this older lower unit in my motor (everything else matches up) and if I do should I add the oring to the replacement lower unit or not?
Thanks
Chris

 

[CER79]

Re: ? for Johnson/Evinrude 9.9/15 Lower Unit Experts

bump

 

[Rick.]

Re: ? for Johnson/Evinrude 9.9/15 Lower Unit Experts

The O ring is there to stop water from getting into the spline connection and rusting the connection. I would think it couldn't hurt to put it on for your new situation. When you grease the drive shaft make sure you put on the splines and not the end of the shaft. On the end of the shaft it can cause a sort of hydrolicly (sp) lock and you will not be able to push it on all the way which will cause further problems when you bolt up the leg. All the best. Rick.