Despite being unable to keep The Iron in the Third Division the following season, this promotion was enough to persuade arch-rivals Grimsby Town of Ashman's talents and they duly poached him as manager in June 1973. It was claimed that Ashman "never enjoyed the same admiration he had gained in Scunthorpe", but in his only full season in charge at Blundell Park, 1971-72 Ron led The Mariners to a very respectable 6th-place finish in the Third Division. But with Town sat a disappointing 18th the following February, Ashman was duly relieved of his services.