1987 Johnson/Evinrude CU Outboards 35A thru 55 Service Manual, Page 250Get this manual
1Visual Inspection The first step in determining the condition of battery should be visual inspectionConditions such as broken, cracked or distorted case; loose terminals, or evidence of electrolyte seepage 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 necessaryCheck 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 in the electrolyte[2Hydrometer
INote Disconnect
battery
positive battery cable whenever charging