I bought an old riding lawn mower (B&S 12HP). To start it, I had to jump it from a car. The battery also looked old, so I replaced it with a new one. When I tried to start it with the new battery, all I got was a little half-turn sound from the engine, and then nothing. Subsequent attempts yielded nothing.
I assumed that since I had been able to jump the mower from a car, all I should need would be a new battery.
I tested the old battery's voltage with a multimeter and got 5V. I tested the new one and got 12V. That's the limit of my diagnostic skills.
Any suggestions for what to look at next?