Honda BF50 (5HP) BF5A Outboard Motors Shop Manual., Page 76Get this manual
XOD XNA 2COOLING SYSTEM
aWATER CIRCULATION
Water enters the inlet in the front of the gear caseThe water pump, located just above the gear case pumps the water through tube in the extension case to the engine, where it circulates through water jacket surrounding the cylinder and cylinder headWater leaves the engine water jacket by draining through the water check hole and by flowing through the thermostat to the exhaust manifoldWater flowing from the exhaust manifold mixes with the exhaust in the extension case and exits through the exhaust port above the propeller
bWATER PUMP
The water pump is an impeller type driven by the pinion shaft and located in the gear case