One pic in the listing shows it stepping out pretty fast and lists a top speed of 17 mph.
A 35 foot boat with 120 hp would I think need a Jesus miracle to plane. My 28 1/2 foot boat with its old motor of 240 hp couldn't plane, top speed of 11 knots. With my new motor of 350 hp, it will plane.
Welcome!! I saw that ad for the Roughwater, looks well maintained and she's a beauty!! Hope to see you up there, my favorite cruising grounds. As others have said, the ER looks spotless, you are off to a great start.