2005 Yamaha F90TR 90HP Outboards Factory Service Manual, Page 104Get this manual
Exhaust cover
Removing the exhaust cover
1Remove the exhaust cover bolts in the sequence shown
Installing the exhaust cover
1Install new gasket and the exhaust cover2Install the bolts, and then tighten them to the specified torques in two stages and in the sequence shown
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2Remove the exhaust cover
Checking the pressure control valve
1Remove the pressure control valve2Check the pressure control valve for wear or damageReplace if necessary3Check the grommet for deformationReplace if necessary4Check the spring for fatigue or deformationReplace if necessary