1995 Johnson/Evinrude Outboards 50 thru 70 3-cylinder Service Manual, Page 235Get this manual
Battery Testing
Battery electrolyte is acidichandle with careIf electrolyte contacts any part of the body, immediately flush with water and seek medical attention1Visual Inspection
The first step in determining the condition of battery should be visual inspectionLook for conditions such as damage to the case, loose terminals, evidence of 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 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 positive battery cable whenever charging batThis test can only be used when there is sufficient electrolyte above the battery plates to fill the hydrometer tubeDo not, however, take readings immediately after refilling the cells with waterThe battery must be charged, then checked with hydrometerView the hydrometer with your eye on the same level with the liquid surfaceThe float of the hydrometer must be freeMake correction for the temperatureSpecific gravity will vary points (0.004) with every 10F (6C) temperature changeFor each 1QF (6C) below 80F (2rC), subtract points from hydrometer readingFor each 1QF (6C) above 80F (2rC), add points to hydrometer readingAfter correcting to 80F (2rC), interpret readings as follows: All cell readings uniform and above 1.225 specific gravity indicates battery is serviceable but may require charging All cell readings uniform and below 1.225 specific gravity, charge fully and retest Variation of more than 30 points (0.030) specific gravity between any two cells, indicates battery condition is questionableRecharge and retest before replacing batteryE