1988 Johnson Evinrude "CC" 9.9 thru 30 Service Manual, P/N 507660, Page 192Get this manual
6Remove all the screws from the cylinder head water cover, tap it around the edge with soft mallet to break the seal, and then remove itRemove the thermostatsealand spring Then, remove the cylinder head7With number punches, mark the top piston dome "No.1" and the bottom piston dome "No.2 8Remove the inner and outer exhaust covers; carefully separate the pieces and clean the gasket surfaces
INote pitting the innerthe cover cover for pitting and and replace Check exhaust flatnessIf exists or is warped, discard it