I have 2 B&S Power Built engines from lawn/garden tractors. One is a 12.5 hp, Model 28U707, Type 1113-E1, Code 990424ZE. The other is a 12 hp, Model 283707, Type 0147-01, Code 92031031. The 12.5 hp is dead and I would like to replace it with the 12 hp but do not know if they are interchangeable? Any help/guidance would be appreciated.