Honda BF35A-BF45A Outboard Motors Shop Manual., Page 54Get this manual
HONDA BF35AA
CARBURETOR SYNCHRONIZATION
Start the engine and allow it to warm up normal operating temperature11 Place the outboard motor on level surface and move the shift lever to "N" position2Remove the three 10 mrn plugs from the intake port of each cylinder
5 10 mm PLUG (3)
3)Attach the vacuum gauge adapters each plug holesConnect the vacuum gauge tubes the adapters
Connect the vacuum gauge No1 tube the No1 carburetor adaptor, vacuum gauge No2 tube to the No2 carburetor adaptor, and the No3 tube the No3 carburetor adaptor properly