2005 Yamaha F90TR 90HP Outboards Factory Service Manual, Page 35Get this manual
Periodic checks and adjustments
5Check the spark plug gap aAdjust if out of specification
Specified spark plug: LFR5A-11 (NGK) Spark plug gap a: 1.01.1 mm (0.0390.043 in)
S6D83080
6Install the spark plugs, tighten them finger tight, then to the specified torque using spark plug wrenchSpark plug: 25 Nm (2.5 kgfm, 18.4 ftlb)
3Suspend the thermostat in container of water4Place thermometer in the water and slowly heat the water