Is a motor that uses 17 amps to much on 20 amp fuse?

yes

for continuous duty it must be at least 10% larger than the normal load

they usually get you on water heaters that take 28 amps need to put those on a 40A with #8 wire not good on the 30A

now if a motor rated fuse and nothing else will ever be on the circuit you can probably be correct with a 17 amp fuse and that is suitable for all the motor overload and locked rotor protection

and it will provide 80 amps for starting