What Scrat says is true. Pull your cover off. If it's like my 40 mariner it should have a small cable that attaches to shift linkage and the safety lock. Make sure it is in neutral and their should be a adjustment on one end of the cable. Those Mariner motors have a lot of compression. Both my 40 and my 8 are hard to pull. My 40 is electric and rope pull. I have never been able to pull start the 40. It would take real hoss to pull start that thing.
Proud Member of Team Geezer
Charlie Weaver USN/ENC 1965-1979