1987 Johnson/Evinrude CU Outboards 35A thru 55 Service Manual, Page 257Get this manual
161 Starter System Voltage Drop Test
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 can be located below
Disconnect the charge coil connector to prevent accidental starting while testing
Clean and retighten, or replace, any connection, cable, or component having greater than specified voltage drop
1Connect voltmeter positive lead to battery positive postConnect voltmeter negative lead to starter solenoid positive terminalTurn key switch to "Start" to crank engineVoltage reading should not exceed 0.3 voltis cranking, otherwise damage to the voltmeter may occur