You know the head gasket or shim is probably there, it's just they are hard to see if your not familiar with what they look like. When you look at the head they can appear as part of the head itself as they are a shiny aluminum shim that usually sticks to the head. Maybe check closer. Definately go with the bigger prop as recomended and once you get the low end needle set some of the vibrations will smooth out.....Gary