Force 125HP Engine

[Devin3200]

Hello first time posting here. I've enjoyed and have found this site very helpful on my restore journey. I have a force 125 engine. L Drive setup on an 89 Bayliner. I'm trying to replace my exhaust gasket. Oh the wonders of and old boat. ( i broke a few bolt heads) No biggie. But after removing the 20 bolts that support the manifold, Its giving me fits to get it to seperate from the case. Any suggestion are to an easy solution or even aggressive solution that will not damage the case or the manifold.

Thanks