1999 "EE" 90, 115 FFI, 150, 175 V4, V6 FFI Outboards Service Manual, P/N 787024, Page 37Get 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 increaseINotellf any anode has been reduced to 9"3 its original size (13 eroded), it must be replaced!
Test for proper installation of the anodeCalibrate an ohmmeter on high ohms scaleConnect one meter lead to powerhead ground and the other lead to the anodeBe sure the surface of the anode is clean to make good contactThe ohmmeter should show low readingIf not, remove the anode and clean the area where the anode is installed The mounting screws and the anode itself should also be cleanedInstall and retest