"The 15 amp fuse" does not describe the circuit that the fuse is protecting.
A fuse is there to protect the wiring in case a device fails. For example, if the fuse is protecting the fuel pump circuit, it's probable that the fuel pump has failed and is drawing too much current. That would be the circumstance with whatever circuit the fuse is protecting; there is either a damaged wire and it is making contact with the frame.
Need to know which 20 Amp fuse is blowing.
It will draw over 18 amps and will blow a 15 amp fuse.
Probably a short to ground.
The 1965 Chevrolet Impala SS fuse box requires a 20 amp fuse for the taillights. A 30 amp fuse can be used when a 20 amp fuse is not available.
The starter is failing.
You cannot because a five amp fuse would blow because the original fuse was seven point five. and a ten amp fuse would not blow quick enough to save or even be safe to use it in whatever you are using it for.
There is a fuse in the fuse box, a relay in the relay center and a pump in the tank. fuse is under the hood on passenger side by hvac box it has a cap on it should be a 15 amp fuse
If you do that the likelihood is that you will blow the 3A fuse quickly. There is a reason why the current fuse is what it is, because it is expecting currents around 80% of 13 A or around 10 A.
Wrong amp of fuse
Check fuse #34 in the passenger compartment fuse panel. It is a 20 amp fuse. It is YELLOW.
The 13 amp fuse with blow at the lower rate to the 15 amp fuse. And At 15 amp the motor is normally more powerful - check the wattage used in both
not smart to do it cant carry the load of the circuit it will blow. in emergency maybe but never go with a higher rating