Honda BF50 (5HP) BF5A Outboard Motors Shop Manual., Page 64Get this manual
HONDA IMPELLER PUMP
[3] IMPELLER HOUSING
ASSEMBLY: Align the flat surface in the center of the pump with the' flat side of the pinion shaft
[I] 28 mm HEX BOLT (4)
[2] WATER TUBE SEAL RING
1 ASSEMBLY:
CK #10 to the thread