I'm doing maint. on my '56 Evinrude Big Twin 30hp. I spent the last 2 years (I'm a bit slow) getting it running again and it runs great. Anyway, I was going to take off the lower unit to change the seals in the gearcase & replace the impellar. However, I'm having trouble getting the lower unit detached from the upper part. At first I forgot to disconnect the shifting linkage but I have since removed the lock screw in the clamp that attaches the upper & lower shift rods. The lower unit still won't come off. I didn't want to force it. Do I need to or am I forgetting to do something else? I just did this last year & didn't have any problem.