1990 Johnson Evinrude "ES" 60 thru 70 Service Manual, P/N 507873, Page 218Get this manual
3Capacity Test Satisfactory capacity tests can be made only when the battery electrolyte equals or exceeds 1.225 specific gravity at 80 (2r C) l]] 4ill
Terminal Voltage Test
Use extreme caution during any load testingImproper procedures could overheat battery and cause electrolyte gassingThis might create an explosive atmosphereaVariable Load High Rate Discharge Tester (Recommended)