Honda BF20A-BF25A, BF25D-BF30D Outboard Motors Shop Manual., Page 242Get this manual
5TROUBLESHOOTING aENGINE
Hard Starting
No fuel in the tank Sufficient fuel in the tankLoosen the carburetor drain screw and check whether fuel reached the carburetorNot reaching the carburetor4 Add fuel and start the engineCheck for collapsed or pinched fuel lineCheck that the fuel tank vent knob is openCheck for air leaks past primer bulbSqueeze the primer bulb and be sure that the fuel is reaching each part of the fuel systemCheck for clogged fuel tubes, strainer and connectorReplace the fuel pump (P5-129
Reaching the carburetorI
Disconnect the spark plugs and check for wet or fouled electrode
Check for blockage in the carburetor
Perform spark test (P2-13l)
If excessively wet, check the carburetor for floodingClean the electrode and restart the engineIf the engine does not restart, try to start the engine with the throttle 14 openIf the engine does not start yet, open the throttle gradually wider and determine the throttle position where the engine starts