1985 OMC 65, 100 and 155 HP Models Commercial Service Manual, PN 507450-D, Page 226Get this manual
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Thermostat Service55
Removal
There is thermostat and pressure release valve in each cylinder headService each thermostat as follows:
1Loosen, but do not remove the four thermostat cover screwsTap the cover lightly to break the gasket sealerCarefu lIy remove the four cover screws the cover and the pressure release valve spring 2Remove and inspect the thermostat and the pressure release valve Also inspect the pressure release valve spring that was removed with the cover3Remove the cylinder head cover to inspect the pressure release valve seat and washer Cleaning, Inspection and Repair