1991 Johnson/Evinrude Models "EI" 40 thru 55 Service Manual, Page 261Get this manual
3Capacity Test 4Terminal Voltage Test
ill procedures
Use extreme caution during any load testingImproper could overheat battery and cause electrolyte gassingThis might cause an explosive atmosphere
aVariable Load High Rate Discharge Tester (Recommended) Connect tester to battery terminal postsDischarge at rate of three times battery ampere hour rating for 15 secondsIf the voltage is 9.6 volts or higher at the end of 15 seconds, the battery has good output capacitybFixed Resistance Tester This equipment has built-in load for high-rate discharge testingFollow equipment manufacturer's instructions regarding test period and meter readingscEngine Load for Resistance Twist and remove the spark plug leadsConnect voltmeter across the batteryCrank engine for 15 secondsIf voltage is 9.6 volts or higher at the end of 15 seconds, the battery has good output capacity