1993 Johnson Evinrude "ET" 90 degrees CV Service Manual, P/N 508285, Page 129Get this manual
Thermostat Service
INotel The thermostats and the pressure valves should be serviced when the powerhead is removed from the adapterRemoval
The thermostats and the pressure valves are attached to the exhaust housing adapterService as follows: 1Remove cover screwsTap thermostat cover lightly to break gasket sealer and remove cover
2Remove gaskets, thermostats, grommets, springs, and pressure valvesDiscard gaskets and grommetsCleaning and Inspection