2001 Mercury 15HGP four stroke can't get cylinder head off

[Jethronone]

I am trying to check and replace the cylinder head gasket of my 15HP four stroke. I have followed the manual and have the cylinder head loose with the top dowel removed. However I can't get the cylinder head off because the oil pump on the bottom hits the frame before the the bottom dowel is clear. Any trick to this? Do I have to remove the whole power head from the frame to remove the cylinder head?
There doesn't appear to be any way to access the oil pump with cylinder head still on
Apologies the photo is sideways!