Was running my 76 18' Classic with 3/4 tank of fuel, and four adults on board on Lake Jackson today. I didn't get crazy with trim because of the passengers, it ran 68 mph on my friends GPS on his smart phone. Running a 383 SBC, TRS 280, 21P Laser II prop. Had full load of extra life vests, two anchors, safety gear two fire extinguishers, etc. Don't know the exact RPM's because the Tach has been acting up, goes to about 2500 and stays there. Going to get the tach fixed, make a run with just me, light load of fuel, an bare minimum to be legal and safe to see what she'll do.
L8R,
Sid