Greetings,
I commited a cardinal sin and now I will pay for it. The sin was agreeing to work on a friends old merc in the middle of summer. As expected, I got bit when I stuck my hand in it, and now I'm on the hook to get it going.
It's a 87 merc 90 outboard. Started off as a simple water pump replacement. When I was finished, I looked up inside the upperdriveshaft housing before restabbing the lower end and sure enough saw the upper seal off its seat and sitting sideways. It appears to be a metal sleeve with a rubber seal on the id which the driveshaft passes through. It also looks like it is pressed in place from above. Info I am finding on line is sketchy. I was hoping to drop the housing away from the powerhead to access that seal and reinstall, but from what I see it appears that cant be done without removing the top end first.
Anyone have any experience with this old timer? Is there a way to reinstall that seal that I am not aware of? Any help is greatly appreciated. Thanks guys.

I have the OEM Mercury service manual for this most likely and ton more for all other outboard apps. it might make his & your life easier to work on this and for future use. 46 bucks shipped to your door. Will need the engine serial # to get you the correct OEM Mercury service manual. Make him pay for the manual. Good luck.

It is the lower seal and carrier. The powerhead will have to be removed to properly access the bottom of the block. Use the OEM style lifting ring and you should have it off in ten minuets. If there is a lot off corrosion then it may take longer. Check the compression, because if the seal has been damaged for a while there is an air leak that can lean out the bottom cylinder causing damage. So not repairing it will lead to damage. Just had to pull one to free up the frozen shift rod just under the powerhead assembly, goes quick. I do not know how west you are but I am on the Cape. Let me know if I can help.

Really appreciate the info. Makes sense now. Didn't even consider that was the lower crank seal I was seeing up there laying loose. At first glance it appeared to be a driveshaft housing seal that popped loose. I still think in terms of I.O. and figured it was an upper oil seal for the driveshaft. Not the seal attached to the powerhead itself. I understand the lean condition issue this would present, and will break out the comp. tester for a quick check as well. Thanks for the response. At least I know what I'm going after now. This is going to raise my buddies fee to at least a case of beer now.