The only thing sinful about masturbation is the lustful thoughts, and it's totally possible to masturbate without lustful thoughts, therefore Jesus totally could have masturbated, and I say he probably did.
BTW if you google images "jesus masturbating" there's a picture of him masturbating and that's more than enough proof for me. I don't think it's photoshopped cause they didn't have photoshop in Jesus's days.