2007-2009 Yamaha F15/F20 Outboard Service Manual, Page 268Get this manual
Troubleshooting the power unit Symptom 1: Unstable engine idle speed, poor acceleration, poor performance, limited engine speed, or engine stalls Symptom Intermittent spark Cause Spark plug malfunction Spark plug cap malfunction Ignition coil malfunction Engine stop lanyard switch malfunction Charge coil malfunction Pulser coil malfunction CDI unit malfunction Incorrect fuel amount supplied Pinched or kinked fuel hose Clogged fuel filter Fuel pump malfunction Carburetor malfunction Cause Throttle stop screw not adjusted correctly Pilot screw not adjusted correctly Malfunction of the carburetor internal parts Prime Start system malfunction Prime Start malfunction Power bobbin malfunction Checking step Check the spark plugCheck the spark plug capCheck the ignition coilCheck the engine stop lanyard switchCheck the charge coilCheck the pulser coilCheck the CDI unitCheck the fuel hoses and fuel hose jointClean or replace the fuel filterDisassemble and check the fuel pumpAdjust the throttle stop screwAdjust the pilot screwDisassemble and check the carburetorCheck the Prime StartCheck the power bobbinRefer to page 3-5 8-22 8-22 8-24