Hello i have a questions on a used mower i just bought. Its a 52 inch scag walk behind. I do not know the model number. The guy i bought it from said is came with a 18 hp briggs and stratton v-twin but blew up when he owned it. He then went to a used mower shop and bought a used 16 hp v twin briggs and stratton. After the 16 hp motor was put on he said it wasn't enough to run the hydros and blades so he added a battery used to engage the blades. My questions is is the 16 hp motor not enough or is there problem with the charging system? i just don't know much about motors but wouldn't think 2 hp would make that big of a difference. Any help is much appreciated.