Depends on the current rating which should be on the motor.
The current caring capacity of a wire is based on the physical size of the wire. The larger the diameter of the wire the more amperage the wire is allowed to carry.
How to calculate a cable size of 3kw motor
30 amp breaker with #10 gauge copper wire
12
Wire size for any piece of equipment is based on the equipments load amperage. The higher the amperage that larger the wire size has to be. For motor loads the motor's amperage has to be increased by 25% to size the conductor. Example, a 10 amp motor load current plus 25% equals 12.5 amps. This would boost the wire size from a #14 to a #12 conductor. This additional amperage increasing is also used for transformer conductor sizing.
A motor can be reckoned at 1.6 kVA per horse-power, so on a 415 v 3-phase suppy the current for 20 HP would be 45 amps. For continuous use the wire size should be 25 mm2
Wire size is based on the amperage of the load. Without knowing what the motors's full load amperage is, an answer can not be given.
The ground wire size is determined from the current carrying capacity of the motor feeders.
The size of wire needed for a trolling motor depends on the motor's maximum amperage draw and the length of the wire run. A general guideline for a 12V trolling motor is 6-gauge wire for runs up to 10 feet, 4-gauge wire for runs up to 20 feet, and 2-gauge wire for runs over 20 feet to minimize voltage drop and ensure proper performance. Be sure to consult the manufacturer's recommendations for your specific trolling motor.
For a 7.5 hp motor operating at 240V, you would typically use a 14-gauge wire and a 40 amp breaker. However, it is best to consult the motor's specifications and the National Electrical Code to determine the exact wire size and breaker needed for your specific setup.
12/2 with ground.
You will need AWG #3 if it is a short run.