1970 Evinrude Ski-Twin, Ski-Twin Electric 33 HP Service Manual 4687, Page 67Get this manual
If the battery is found to be good after boosting, it
should be fully recharged before returning it to serviceIf none of the cells come up to 1.95 volts after the first boost charge, the battery should be given second boostBatteries which do not come up after second boost charge should be replacedBATTERY CHARGING Boost charge 12-volt batteries at 50 amperes for 20 minutes (1000 ampere minutes)If the charger will not give this rate, charge for an equal number of ampere minutes at best rate availableDO NOT boost battery more than this amount for the "light load test"If batteries are to be fully charged by means of a