1987 Johnson/Evinrude CU Outboards 35A thru 55 Service Manual, Page 249Get this manual
Battery Specifications
INo All batteries should be of heavy duty, marine construction The battery must not be maintenance-free sealed type
35 thru 50
For best performance, we recommend 12-volt battery with minimum rating of 360 amps cold cranking at (-18 C) and 115 minutes reserve capacity at 80F (27C)Battery Testing Battery electrolyte is an acidic solution and should be handled with careIf electrolyte contacts any part of the body, immediately flush the exposed area with liberal amounts of water and seek medical aid as soon as possible