1998 Johnson Evinrude "EC" 90, 115 SPL Service Manual, P/N 520209, Page 134Get this manual
Thermostat Service
INote 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 cover2Remove gaskets, thermostats, grommets, springs, and pressure valvesDiscard gaskets and grommetsCleaning and Inspection