1997 Johnson Evinrude "EU" 90 thru 115 90 CV Service Manual, P/N 507267, Page 229Get this manual
Starter System Voltage Drop Test
By making systematic check of the starter system, any component or electrical connection having excessive resistance can be located
11 Avoid
accidental starting of engine while servicing; twist and remove all spark plug leadsClean 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 voltStep 2, connect the voltmeter leads only while the engine is cranking, or damage to the voltmeter can occur