Tony, You may have already discovered that the WN7A (Powermatic 12) is a mashup created using major components of two Mercury motors. The powerhead is essentially a Mark25 and the lower unit is essentially the Mark20/KH7. If you do internet searches for these Mercury motors you will find a number of sources for manuals and parts. I have pdf copies of both the Mark 20/KH7 and the Mark 25 parts manuals as well as the the Mercury Outboard Service Manual for all models 1940-1965. I don't think I paid anything for these but I cannot remember where I got them - old timer's Disease setting in!