If you are using an amp, check how fast the T/R relay is. Acom and similar amps are around 6-10 ms. I'd suggest you set it to at least that much or 15 ms to be on the safe side. Again, assuming you use an amp, find out what the relay timing is.
With any amplifier, start with a higher delay (say 30ms) and a second receiver listening to your signal, then send a string of Vs or dots. Bring down the delay until clicks start to appear. That setting is the first sign of hot keying; increase the delay slightly and that becomes your optimum value.