1963-1973 Mercruiser all Engines and Drives Service Manual Books 1 and 2, Page 251Get this manual
Quality of the image is intentionally reduced!
3 Reverse test ead and note reading on meter4 If both read inas are zero or very high, diod is defe ct iv eA good dio de will give on low reading and one high ading 3 Place other tester lead on tator