1991 Yamaha Outboard Factory Service Manual 9.9 and 15 HP, Page 92Get this manual
INSPECTION, CLEANING AND REPAIR Wash component parts in solvent and blow them dry with compressed airWater pump 1Check the water inlet cover for clogging with dirt2Check the water pump joints for air leaks3Check the impeller for wear4Check the cartridge outer plate for wear and scratchesGears and bearings 1Check the forward, reverse, and pinion gears for wear and damageNOTE:_ If anyone of gears is damaged, it should be replaced as an assembly 3Check the propeller shaft spl ines for wear4Check the clutch dog and splines for wear
5Check the compression spring for fatigue, and check the plunger for wear
6Check the propeller blades and splines
for wear and scratches
7Check the propeller nut (castle type) for
damage on threadsDrive shaft 1Check the drive shaft for runoutPlace the drive shaft on V-blocks, anti measure the drive shaft runout with dial gaugeMaximum drive shaft runout: A: 0.3 mm (0.0118 in) B: 0.2 mm (0.0079 in)
2Check the tapered roller bearing, needle