Yamaha Marine Outboards F4A/F4 Factory Service Manual, Page 218Get this manual
WATER PUMP
SERVICE POINTS
Water pump housing inspection 1Inspect: 9Water pump housing 9Outer plate cartridge CrackTwistScratchDamage Replace
2Inspect:
CrackTwistScratchDamage Replace
Impeller and insert cartridge inspection 1Inspect:
9Impeller 9Insert cartridge
CrackDistortionBurningDamage Replace