Is there a reliable test, mine seems fine when u wind it ut turns the prop but i has two instances of engaging the starter put the prop only moves a few inches, could not hear stater continuing to run, stater bench checks ok adapter does not slip when wound with a screwdriver
Any ideas what could have caused it no loose connections
What is the voltage of the battery? How old is the battery?
A couple years old is kept on battery tender, no prob with battery
But, you haven’t put a voltmeter on the battery, nor have you tested it for capacity.
In addition, you haven’t measured voltage at the starter while under load.
You don’t know what’s good without logical troubleshooting.
I had a similar problem last annual. Could not duplicate the problem during repeated starts, however the battery did not pass a capacitance check. I replaced the battery and have had no problems in nine months. Battery was 4 years old.
But it started after it cooled some
Adapter seems to be ok, grips and turns the prop and you can not turn the prop backwards.
I think we have a starter or solenoid problem when it gets heat soakes
Check the easy things first, cap check the battery. No reason to go hunting with expensive parts and troubleshooting before knocking the easy items off the list. @TonyWilliams and @rpmoll gave you the correct information.
Just had a friend swear to me his lawnmower starter was going out, wanted to check everything under the sun, same symptoms as you describe. I heard it start one time and immediately said time for a new battery, let’s test with a new one, sure enough that was it. He stated the battery was 1 yr old, until we looked at it, and the date code said 5yrs old 