According to Mercury Parts Manual Mark 25/25E used 3 variations of Phelon
Magneto...which may or may not make any difference. What might clear matters
up is a part number by part number comparison of the Phelon magnetos involved. If member of AOMCI you can use site magneto catalog otherwise
it is fit and try or hope to hear from someone who has been there/done that.
WG7 corresponds to KG7 so maybe that is a more likely source. At some point
Mercury changed from a separate cam to a cam ground into crankshaft...manual
shows two Mk 25 crankshafts...these matters are way outside my experience