1998 Johnson Evinrude "EC" 90, 115 SPL Service Manual, P/N 520209, Page 225Get this manual
Battery Specifications
For each motor, provide one battery that is: 12-volt, heavy-duty, designated "marine" Ventedrefillable or maintenance-free Rated 360 CCA (465 MCA) with 90 minutes reserve 50 amp-hr
Deep-cycle batteries are suitable IF they meet or exceed the minimum CCA requirementsInstalling and Connecting Batteries and Cables
Place the battery so it is easily accessible for frequent checking and recharging and in hold-down systemInstall positive cable to positive post and negative cable to negative post
When connecting to the battery, begin by placing largesurface starwasher over the threaded battery post, then stack cables from accessories, then cables from the motorFinish the connection with hex nut, tightened firmly with wrench