1990 Johnson Evinrude "ES" Colt/Junior thru 8 Service Manual, P/N 507870, Page 43Get this manual
AnodesTesting and Replacement Erosion or disintegration in salt or brackish water indicates the anodes are performing their functionThe anodes should be inspected andor replaced at intervals or corrosion of the engine will increasef51 '6l
If any anode has been reduced to two-thirds its original size (one-third eroded), it must be replaced! Test for proper installation of the anode Set an ohmmeter
E.J to low ohms scaleConnect one lead of the ohmmeter to