I spoke to the owner earlier today.
I'm "pretty sure" the engine is a 6BTA 315.
Boat has a 1.5:1 gear, 20X22 4 blade.
Easy cruise of 18 knots @ 2100 rpm.
20-22 knots 2300-2400 depending on tide/current.
He said the boat will plow through any (reasonable) sea conditions @ 18 knots with zero pounding.
Of course his primary boat is a 30 knot planing hull.