Former boss Young moved into a Director of Football role at the end of the season after seven years in the dugout at the club.
Now they've turned to a former player and captain in Grant - who recently retired from playing - to lead their charge next season in the National League North.
The 34-year-old has had a short stint as a manager already having been Radcliffe manager between 2021 and 2023 and now steps back into the world of management again.
He is a much-loved face among the Mariners faithful and says the chance to return excites him.
Grant said: “I’m absolutely delighted. It’s a massive opportunity.
"When I went for the interview with Neil (Young) and James (Leary), the vision the club have got moving forward, the structure the club have now put in place with Neil going into the role he’s gone in, it really did excite me.”
Director of Football Young said it was vital the club had someone who was familiar take the reins.
“There has been lots of work done over many years, and even more so in the last couple of seasons from a team perspective," the former boss said.
"It was fundamental that we brought someone into the role who understands the club and how we play with our current squad.
“Continuity for the players was absolutely key, and Bobby fits that role perfectly.
“We all know his personality is infectious and his desire and determination to become the Marine manager was clear to see.
“I think we can work really well together and over the next 12 months, build on what has gone before and make it even better.”