Friend of mine has a 10515 electric start machine. His battery was bad, so he went to a battery shop locally and bought a sealed aftermarket battery. It's the right voltage and seems to turn the engine over fairly well, but it won't start. When pulling starter rope it fires right up. I am going to try charging the battery before digging into this in the next couple of days to see if the charger is getting the battery up to capacity. I have a feeling that it might not have the amperage to turn the engine over fast enough. In the meanwhile, I thought I'd check with you guys and see if anyone has run into this scenario previously.