1992 Johnson Evinrude "EN" 9.9 thru 30 Service Manual, P/N 508142, Page 288Get this manual
Battery Specifications All batteries should be of heavy duty, marine constructionThe battery must be vented, refillable typeDeep-cycle batteries must not be used as the engine's cranking batteryA battery that is not fully charged or less than recommended capacity may not crank the engine fast enough to produce ignition component output
9.9 thru 30 For best performance, OMC recommends you use 12-volt battery with minimum rating of 350 cold cranking amps (eeA) at (70 amphrsat -18 e) and 100 minutes reserve capacity at 80 (2]0 e)