Small Engine Troubleshooting Problems? Ask a Mechanic Now.
It can be starter or solenoid problem, but battery cable connections will do the same thing.
The starter solenoid/relay would be the common problem for intermittent starts. It would not make good contact and it is the connection between the battery and the starter.
What engine is this? What is voltage drop across the battery when starter is turning? 165 and 68 amps seems high for typical gas mower engine. I would not have expected that much.??
Starter drive should not slip! It would need to be replaced!