Used a flank steak marinade on the New York end of a mule deer strap. Soy sauce, garlic, olive oil, vinegar, pepper and Worcestershire sauce. It was in the liquid for 24 hours, should have done 48. Still came out pretty well.
>>>Soy sauce, garlic, olive oil, vinegar, pepper and Worcestershire sauce.<<<
You can never go wrong with that mixture.
When I'm marinating thicker cuts like elk backstrap I've started cutting the piece lengthwise and making two long 1" thick steaks (resemble flank) which take the marinade better and cook quickly for med rare. My go-to is a fajita marinade recipe.
I agree with Hank Shaw that prolonged marinating doesn't really penetrate a thick cut any further but just makes the surface extra tender (or mushy).