The larger the prop the more work it has to do. Work equals heat. Heat equals bad. You need to get a prop that is called for by the motor maker. They have tested it with different props and battery voltage and they will give you a list of props that will work with that motor and battery voltage. Try and stay in this range. Putting to big a prop on a motor is like driving up a hill in third gear instead of second. You can go slower, but the motor is still working to hard and you need to shift down. Proping a motor is like gearing a car, you want it to do the work, but not lug it down in the process. Drop down on the prop and everything should be OK.
Ed