1990 Johnson Evinrude 120 thru 140, 185 thru 225, 300 HP, P/N 507875, Page 340Get this manual
Cranking Discharge Method 1Check battery voltage If voltage is greater than 12.5 volts, go to step If voltage is less than 12.5 volts, go to step 32Separate the ignition charge coil connectorsCrank engine in short bursts until battery voltage is less than 12.5 voltsCheck battery voltage with key in the "Off" position INotel
engine battery cables before proceeding with this check
3Connect to 40 amp ammeter in series between the rectifier regulator red lead and the battery side of the starter solenoid4Reconnect the engine's battery cablesReconnect the ignition charge coil connectorsThe rectifierregulator requires battery voltage on the purpie lead to operateBefore proceeding, verify battery voltage at terminal strip purple leads when key is ON
5 Start the engine and run at approximately 4500 rpmThe engine's ammeter should indicate nearly full outputor 35 ampsAs you continue to run at 4500 rpm, the voltage should stabilize at approximately 14.5 volts and the alternator output should begin to decrease