Noone asks for the incoming boarding pass to compare with your outgoing boarding pass and makes decisions based on the similarities between the two. It would be an absolute zoo: you might have a single ticket on two airlines, you might have a single ticket which you think is on a single airline but in fact they are on different operating carriers, you might have two tickets on the same airline and who knows what else combinations are possible given there are no less than three different kinds of carriers (ticketing, marketing and operating). Not to mention that some passengers create, ahem, what to call what some of us do? ... interesting ;) flight itineraries.
No, having the outgoing boarding pass is enough. Online check in typically opens a lot earlier (at least 24 hours but sometimes days or even months) so having an electronic or self printed boarding pass is not at all unusual at nine hours before flight.
There are two possible problems: a) there is no online check in. I do not think you want to fly that airline in 2017 so I will skip this case. I mean, Yakutia have introduced online checkin in 2014 December and it's really, really hard to find a more remote corner of the world than the one they fly. b) if the tickets are not on the same day. Depends on where you transfer and how but if you need to cross security or border guard then they you typically need a same day boarding pass although nighttime flights are sometimes exceptions -- basically, you need to give us more details if the two tickets are on different days if you want us to help.