Honda BF15D BF20D Outboard Motors Shop Manual., Page 186Get this manual
7) Remove the two 36 mm flange bolts and remove the
thermostat cover, cover gasket and thermostat
8) Remove the six 22 mm flange bolts and remove the following:fuse holder bracket- water jacket cover- jacket cover O-ring- water tube seal- flush valve and flush valve spring9) Remove the 20 mm screw and anode[2] THERMOSTAT THERMOSTAT COVER