Re: Changing lower unit oil? (skeeterbrain)
No, you can't overfill it. In fact, you are supposed to fill it until the oil flows out the top. You then put the top plug back in (with the fill tube still connected to the lower hole). This creates a vaccum to keep as much of the oil in as possible when you quickly remove the tube and insert the lower plug.
PS - make sure the engine & lower unit are verticle (the cavitation plates should be level) when you fill the lower unit. Otherwise you will not fill the lower unit completely. And if the oil you drain out was milky looking you have a bad seal and water is getting into the lower unit (which will need to be fixed or you will damage the gearing).
Re: Changing lower unit oil? (skeeterbrain)
You probably need to tilt the unit up a little to get all the old lube out, then lower it to level to insure you get it full.