Size your fuse by the size of the wire not the load. The wire is what you are trying to protect from high current. You don't want the wire to get hot and catch on fire. Find out what size wire you are protecting.
You may wish to check the wire size as well to make sure it is adequate:
Here is a link to current/AWG limits: American Wire Gauge table and AWG Electrical Current Load Limits with skin depth frequencies and wire breaking strength
More than likely your wire is short enough that you can use the max Chassis wire size.
As for the "in rush" or starting current:
When a motor is standing still the current is only restricted by the resistance in the copper. This is very low and the current is very high. As the motor begins to spin an electric field develops that also resists the current and this lowers the draw to the running state. This high current is momentary and will not heat the wire nor blow the fuse unless the motor is slow to start or stalls, in which case you want it to blow the fuse if the current is to high for the wire.