I can fully understand if someone disagrees with masturbation on religious grounds but it is No, lack of concentration is not a side effect of masturbation. I don't.
Separate the 2 activities and indulge in masturbation only when you are naturally feeling the urge. Going cold turkey on watching porn do not.
Masturbation can help you concentrate, though not necessarily because How often should I masturbate for optimum concentration powers?.