1997-2001 25/35hp Johnson 3 cyl - cylinder head differences

[speedfreak]

Does anyone know what the technical difference/s was between the 1996- 2001 model 25hp and 35hp 2 stroke 3 cyl. Johnson/Evinrude cylinder head? 25hp part number shows 0339167 (obsolete/no longer available) and the 35hp part number was 0344228. Appears that was one of the differences between these engines (25hp vs. 35hp).
My engine model # is J25RMEUR, (1997 model).