1985 OMC 65, 100 and 155 HP Models Commercial Service Manual, PN 507450-D, Page 338Get this manual
Starter System Voltage Drop Test All Models
By making systematic check from the positive battery terminal, through the starting circuit and back to the negative battery terminal, any component or electrical connection having excessive resistance, thus causing high voltage drop and subsequent hard starting, can be located belowDisconnect the four wire connector between the armaLL ture plate and power pack so that the engine can be cranked without firingConnect voltmeter and turn ignition switch to "Start" to crank engineBy placing voltmeter leads against battery, solenoid, and starter motor terminals rather than against connecting cable ends, each connection can be tested for high resistance along with componentClean and retighten, or replace, any connection, cable, or component having greater than specified voltage drop1Connect voltmeter positive lead to battery positive postConnect voltmeter negative lead to starter solenoid positive terminalTurn key switch to start to crank engineVoltage read ing should not exceed 0.3 volts2Connect voltmeter negative lead to starter solenoid terminal onlyWhile cranking engine, connect voltmeter positive lead to starter solenoid opposite terminalVoltage reading should not exceed 0.2 voltsRemove voltmeter positive lead from starter solenoid and stop cranking engineI the above step, connect the voltmeter leads only while the engine is cranking, otherwise damage to the voltmeter may occur3Connect voltmeter positive lead to starter solenoidstarter lead terminalConnect voltmeter negative lead to starter motor terminalTurn key switch to start engineVoltage reading should not exceed 0.2 volts4Connect voltmeter positive lead to battery negative lead common powerhead ground screwConnect voltmeter negative lead to battery negative postTurn key switch to start engineVoltage reading should not exceed 0.3 volts5Reconnect the four wire connector