t500hps

Depends on if your looking at the speedo or a GPS. My 312 had stock 502 mags and was 8,000 lbs dry. Regularly saw 76-77 on the speedo, but the GPS was 71-73 (my bottom could have used slight work for better speed). Remember the 312 has a step, but it's a small single step. I figured the extra 55 HP per side will give it another 5-6 MPH. This guys boat should be ready soon.....guess we'll find out then.

t500hps

The 312 is an entirely different boat than your old 311. A good 2 feet shorter, lighter, and looks more narrow at the bow (and the single step is only slightly beneficial). Every 312 I'm aware of had 1.65 drives and 30 pitch 4 blade props when powered by the 454 and 502 mags. I believe the 454/310 had 28 pitch but not sure.