new to boating and have a real dumb Q ?

[snotrocket]

I have a 1976 marlin with a omc 140 we were out in the bay yesterday and it goes really well 30mph @ 3k my question is what is the max rpm I can go I left the engine book on the boat and it 30 miles away from my house so before anyone yells the LOOK IN THE BOOK reply I was hoping someone might know off hand how hard I can push it thanks in advance .......