Re: lower unit will not release - HELP !!!!
It's not fun and you may need to bite the bullet but it can be done.
The drive shaft is splined to the pinion inside the lower unit, however, it is free to slide out. What actually holds it in position is the drive pin for the water pump impeller.
So, if you force off the lower unit, the drive pin will either break off or ruin the top water pump seal and the shaft will just slide out of the lower unit. Both parts are cheap though and at least you will have to bottom off, allowing you better access to the drive shaft. Don't let the oil run out the shaft hole. Now you can try to get it unstuck from the crankshaft. By the way---you did disconnect the shift linkage, didn't you? You must lower the bottom a bit and reach in the gap with a screwdriver or allen wrench (depending on screw type) to remove the connecting screw for the two shift shafts.
You can now try some sort of puller to grab the shaft and an impact hammer to try and pull it out from the crank. BUT: Be aware I have a 20 HP sitting, soaking in PB Blaster for a month and it isn't any closer to coming out. I have time on my side and eventually it will release. I just keep spraying and wiggling the shaft.
