I ran across an outboard on Craigs List that was a rebuilt old Eska leg and lower unit with a new 6.5 HP Tecumseh 4 stroke motor on top in place of the original 2 stroke. It was listed for somewhere around $600, but I just happen to have an old 7.5 HP Ted Williams (Eska) sitting around. Have any of you done this type of conversion? What is involved?