1990 Johnson Evinrude "ES" 9.9 thru 30 Service Manual, P/N 507871, Page 164Get 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 thermostatseal ,and spring Then, remove the cyl nder headand the bottom piston dome "No.2
1201 With number punches, mark the top piston dome "No1"
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