can a riding mower with a briggs 12 hp 283707 engine be replaced by a briggs 14.5 hp 287707 engine?

the 14.5 hp is an engine only so the carb and intake would have to be used from the 12hp broken engine.

kpr, April 2009

Short answer - no.

The basic engine will bolt straight on, and the carb will physically fit, but the jet and venturi sizes will be wrong. It will run over-rich. If the carb has adjustable jets, you may be able to compensate for full power runnng, but it won't run properly at intermediate power settings.

Phil Saunders, April 2009