1994 Johnson/Evinrude "ER" 9.9 thru 30 outboards Service Manual, Page 290Get this manual
1Visual Inspection The first step in determining the condition of battery should be visual inspectionLook for conditions such as damage to the case, loose terminals, evidencof electrolyte seepage, etcThese signs may indicate improper care, installation, or application of the batteryLook for excessive corrosion on the battery terminals and cablesCheck the battery cables for worn or frayed insulationReplace cables, if necessary842018
Check the electrolyte level in each cellIf electrolyte level is below the plates, it is possible the battery is permanently damagedAlso look for dirt, oil, or other contaminants floating the in electrolyte
[!] 2Hydrometer