1998 Johnson Evinrude EC 50 thru 70 HP 3-Cylinder Service Manual, Page 36Get this manual
AnodesTesting and Replacement Erosion or disintegration in salt or brackish water indicates the anodes are performing their functionThe anodes should be inspected at intervals and replaced when necessary, or corrosion of the engine will increase
INote If
any anode has been reduced to 9'3 its original size (13 eroded), it must be replaced! To increase the duration of the anodic protection, the starboard stern bracket (on some models) is drilled to accept an additional anode