Hi Alvin;
As I've said above, with a stall current of 380 amps and a duty cycle of around 1/30 my motor should have been taking 13A. My mosfet is rated for 190A at 25°C and 130A at 100°C. I don't think any amount more derating is going to help; I should be at 1/14 or 1/10 of the data sheet spec.
I had a problem with my current measurements last time, I think I need to run the scope in roll mode rather than Y-T, it allows for better viewing of the current over time. Then I can verify what the math says about stall current and duty cycle.
Unless my math is wrong; I would be humbled if someone can show me my mistake.
Tomorrow will be a test with a window motor I think. The light bulb suggestions are good but I have no car light bulbs (that I am willing to remove from my car lol)