2005 Yamaha F90TR 90HP Outboards Factory Service Manual, Page 36Get this manual
Power unitControl system Water temperature 5862 (136144 F) above 70 (158 F) Valve lift 0.05 mm (0.0020 in) (valve begins to lift) more than 4.3 mm (0.17 in)
6Install the thermostat and cover7Connect the cooling water hose, and then install the flywheel magnet cover
Control system
Checking the engine idle speed
Checking the cooling water passage
1Check the cooling water inlet cover and cooling water inlet for clogsClean if necessary
1Start the engine and warm it up for minutes2Attach the special service tool to spark plug wire #1 1, and then check the engine idle speed