A jury at Hull Crown Court found Jamie Kendall, of Barnetby Road, Hessle, guilty of 33 counts of sexual abuse from across a 14-year period.
The jury reached a unanimous verdict on Friday (Oct 8) following his trial.
The court heard how Kendall abused a position of trust to manipulate and abuse his four victims over a fourteen year period.
Police said he showed "no repentance" for his actions by pleading guilty and forcing his victims to relive the trauma of their abuse by making the case go to trial.
Humberside Police said Kendall systematically abused his victims by preying on their vulnerabilities for his own sexual gain.
Detective Constable Steve Bromby, of Humberside Police, said: “Firstly, I would like to start by commending the bravery and courage of Kendall’s victims and having the strength to come forward and speak about their horrific experiences.
“Although today’s sentencing is welcomed and Kendall is behind bars where he belongs, it still does not take away the pain he caused his victims.
“I hope that this sentencing can provide his victims with some comfort in knowing that they, and nobody else will come to harm because of this predator.
“I would like to provide reassurance to anyone who may have suffered a sexual abuse, if you come to us we will listen to and support you and act against those responsible.
“We work in partnership with the local authority and a number of local charities and agencies to ensure victims of this type of crime are offered advice and support whether they decide to pursue through the justice system or not.
“If you have been the victim of rape or sexual assault, there are various ways you can report it to the police. You can speak to independent charity Crimestoppers anonymously, or you can report directly through our 101 number, or 999 in an emergency."