Yes you need a pause to pace the servo pulses to approximately 50 per second. In addition, note that Pulsout is only a toggle. Unless you force the pin to a zero at the start of the loop, there is a good chance that sometimes the line will idle high instead of idling low. That drives a servo nuts.

Try
for i = 0 to 20
low servopin
pulseout servopin, 200
pause 18
next i

Note that 95+% of the time you may get away without forcing the servopin low but there WILL be times when the line idles high. It cost me a plane crash.

HTH
Brian